"Man of few words, aren't you?"
- Alyx Vance

Dr. Gordon Freeman, AKA "The One Free Man" was a Research Associate at the Black Mesa Research Facility in Black Mesa, New Mexico, having graduated from the Massachusetts Institute of Technology (MIT) with a PhD in theoretical physics. On the morning of May 16, 200-, however, the Resonance Cascade and following Black Mesa Incident, Seven Hour War, and the Uprising 20 years later turned Gordon from an unassuming scientist to a one-man army and revolutionary leader.

• Hair: Pompadour / Smooth Wave / Clean Cut (whichever you prefer)
  
• Facial hair: Goatee
  
• Hair color: Auburn

• Strength: 8 (Circus Strongman)
  
  Freeman is notably skilled with his crowbar, and carries a large assortment of weapons throughout the series with no trouble.
  
  
• Perception: 4 (Unsuspecting Trout)
  
  Freeman is ambushed or taken by surprise multiple times in the series. However, he is perceptive enough to be somewhat apt with explosives and energy-based Black Mesa/Combine weaponry.
  
  
• Endurance: 5 (Stain-resistant)
  
  Despite surviving the dangers he does throughout the series, this can be attributed to his HEV suit, as without it (or some similar armor), he is shown to be quite vulnerable. Additionally, Freeman is knocked off his feet or even unconscious multiple times in the series.
  
  
• Charisma: 1 (Misanthrope)
  
  Freeman is a silent protagonist, having seemingly never said a word throughout the series. However, following the Black Mesa Incident, he gained a messianic reputation among survivors of the Incident and 7 Hour War, so putting points into Charisma with Intense Training may be desirable.
  
  
• Intelligence: 9 (Genius)
  
  Freeman is an MIT graduate, having received a PhD in theoretical physics and a position as a Research Associate at Black Mesa by the age of 27.
  
  
• Agility: 6 (Catlike)
  
  Unless you consider B-Hopping and ABHing to be canon, Freeman’s agility is only slightly above average, being outmatched by others such as Alyx Vance.
  
  
• Luck: 7 (Lucky 7)
  
  Freeman survived the Resonance Cascade and everything that followed in Black Mesa and City 17, but he didn’t get through it unscathed.

• Guns
  
  Despite having never held a firearm prior to his Hazard Course training (besides a butane-powered tennis ball cannon he built at age 6), Freeman is notably proficient with any type of gun he can get his hands on.
  
  
• Melee Weapons
  
  Freeman’s crowbar is an iconic part of his arsenal, appearing in all games in the mainline series. He uses it to clear anything blocking his path, from wooden boards and crates to soldiers and metrocops.
  
  
• Science
  
  Freeman is a scientist at the Black Mesa Research Facility. Although this skill in particular is primarily used for hacking terminals (something more suited to characters like Alyx), there are a few perks that require a high Science level you might want to take.
  
  
  
  Minor Skills
  
  
• Explosives: Freeman uses a variety of explosives throughout the series, from simple hand grenades to shoulder-mounted rocket launchers.
  
  
• Energy Weapons: Freeman uses some experimental energy weapons in Black Mesa, as well as some manufactured by the Combine in City 17.
  
  
• Medicine: Medkits are Freeman’s saving grace in Black Mesa and City 17, so getting more health from Stimpaks is incredibly useful.
  
  
• Sneak: Although not always the stealthiest, Freeman has been known to employ stealth tactics when needed, such as when avoiding the Tentacles in Silo D or the Gargantuas in Track Control and the Xen Mines.
  
  
  
  Traits
  
  
• Four Eyes: Freeman is almost always seen wearing glasses.
  
  
• Skilled: Freeman is incredibly skilled in multiple fields, from theoretical physics to combat tactics.

• Vault jumpsuit / RobCo jumpsuit / Scientist scrubs (Old World Blues)
  
  
• Followers lab coat / Scientist outfit / Lab technician outfit / Vault lab uniform
  
  
  
• Eyeglasses
  
  
• Power Armor (any kind, ideally no faction, no helmet) / Stealth Suit Mk II (Old World Blues)
  

• 9mm Pistol
  
  
  
• 10mm Pistol / Weathered 10mm Pistol
  
  
• .44 Magnum revolver / Mysterious Magnum (I'm aware the revolver in HL is a .357, but I think the NV .44 looks a lot closer)
  
  
• 9mm SMG
  
  
  
• 10mm SMG
  
  
  
• Hunting Shotgun
  
  
  
• Frag Grenade
  
  
  
• C-4 Plastic Explosive (+Detonator) / Satchel Charge (Lonesome Road)
  
  
  
• Missile Launcher / Annabelle
  
  
  
• Gauss rifle / YCS/186 (Less in function/appearance, more in name)
  
  
  
• Arc Welder (Lonesome Road) / Sprtel-Wood 9700 (Gun Runners' Arsenal)
  
  
  
• (Optional) Police Baton
  
  
  Unfortunately, there are no crowbars in the Mojave, but if you're down for some modding, here are two mods I found that add some:
  
• Punk Crowbar - NV[www.nexusmods.com]: Adds a unique "Punk Crowbar" which can be found in an Average-locked toolbox at Powder Ganger Camp West. Can be repaired with Tire Irons.
  
• Lock-Breaker Crowbar[www.nexusmods.com]: Adds a generic crowbar which is sometimes carried on low-level human enemies throughout the Mojave. As the name suggests, this crowbar has an additional function that can break most non-quest-related locks throughout the Mojave, even those above the players' Lockpick skill. If that's too OP for you, stick to the Punk Crowbar. Some users of the mod report a bug where the "Break Lock" option persists even after dropping the crowbar.
  
  
  
• (Optional) Binoculars (item cut from HL2, replaced with the HEV's suit zoom)
  

• Stimpaks
  
  
  
  
• Nuka-Cola (+variants) / Sunset Sarsaparilla
  
  
  
• (Optional) Ant Nectar / Ant Meat
  
  
  
• Med-X
  
  
  
• Antivenom
  

1. Swift Learner (LV 2)
   Freeman received his PhD at a relatively young age, demonstrating his ability to learn quickly.
   
   
2. Educated (LV 4)
   Freeman is a graduate of MIT with a PhD in theoretical physics, having also briefly visited the University of Innsbruck in Austria.
   
   
3. Entomologist (LV 4, Survival 45)
   Although Freeman isn’t an entomologist himself, he has plenty of experience with large ants from his encounters with Antlions.
   
   
4. Run ‘n Gun (LV 4, Guns/Energy Weapons 45)
   Freeman had to stay moving throughout much of his journey in Black Mesa and City 17 while having to defend himself.
   
   
5. Shotgun Surgeon (LV 6, Guns 45)
   
   
6. Toughness (LV 6)
   
   
7. Scrounger (LV 8)
   Freeman could always find extra ammo for himself in Black Mesa and City 17.
   
   
8. Strong Back (LV 8)
   Freeman carries a plethora of weapons in the series.
   
   
9. Grunt (LV 8, Guns 45, Explosive 20)
   Although not a grunt himself, Freeman’s run-ins with the HECU and Overwatch forces gave him plenty of combat experience.
   
   
10. Super Slam! (LV 8, Melee Weapons 45)
    
    
11. Finesse (LV 10)
    
    
12. Fight the Power! (LV 10)
    Both major titles in the Half-Life saga feature Freeman fighting government forces.
    
    
13. Math Wrath (LV 10, Science 70)
    
    
14. Nerd Rage! (LV 10, Science 50)
    Despite being an unassuming scientist before the incident, Freeman quickly became a one-man army.
    
    
15. Fast Metabolism (LV 12)
    
    
16. Heavyweight (LV 12)
    Some of the weapons Freeman gets his hands on (ie. the RPG & Gravity Gun) are quite heavy, and he uses them with no hassle.
    
    
17. Unstoppable Force (LV 12, Melee Weapons 90)
    Freeman was unstoppable against the US military & Combine forces.
    
    
18. Purifier (LV 14)
    Freeman killed swaths of aliens with his crowbar.
    
    
19. Better Criticals (LV 16, PE 6)
    
    
20. Chem Resistant (LV 16, Medicine 60)
    Freeman was constantly administered morphine and antitoxins by his HEV suit and has seemingly suffered no adverse effects (yet).
    
    
21. Weapon Handling (LV 16)
    
    
22. Just Lucky I’m Alive (LV 50, Neutral Karma)
    Freeman had lots of close calls in his journeys and is lucky to be alive.
    
    
23. Thought You Died (LV 50, Good Karma)
    Many survivors of the Black Mesa Incident and 7 Hour War likely thought Freeman had died in the Incident until he returned to City 17.

(Note: since Just Lucky I’m Alive and Thought You Died are both Level 50 perks, you can only choose one. Up to you!)

“Since Gordon does not say a single word during the entire saga and is almost always in the player's control, it is not clear to what extent he exists as a separate character outside of the player's influence.”
- Combine Overwiki

I think this excerpt puts it pretty succinctly---Freeman's role as a vessel for the player makes it hard to assign him any real personality traits without sinking into the messy realm of headcanon. As such, that's essentially what this section is. However, the headcanon I've built for this guide is based on numerous bits and pieces of information and backstory we get on Freeman throughout the Half-Life series, both in-game (ie. seen by the player or told of by NPCs) and elsewhere (ie. Prima guides or manuals), some of which may be more or less debatable in terms of its canon status.
Essentially, this is a headcanon I think is closest to how Freeman would realistically behave and think given what we've learned about him over the years. However, if you have your own headcanons for Freeman, or you're a big fan of Freeman's Mind or HLVR:AI, and you'd prefer to base your gameplay style off of those, please do so! If not, here you go:

Freeman is an incredibly intelligent man who had an interest in physics and engineering from a young age. It led him to excel in school and eventually visit the University of Innsbruck and graduating from MIT with a PhD in theoretical physics.
Freeman hoped the research he was doing at Black Mesa could eventually have civilian applications, wishing to make the lives of common people easier however he could.
Freeman is a relatively solitary and quiet man, but still befriended coworkers such as Dr. Isaac Kleiner, Dr. Eli Vance, and Officer Barney Calhoun.
When the Resonance Cascade struck, Freeman miraculously survived, and when he realized the gravity of the situation, he put himself in harm's way to protect those in the facility, going as far as to violently resist the US Marines by killing dozens of their soldiers sent to execute all personnel.
When he was told he'd need to travel to the Borderworld to stop the invasion by killing the Nihilanth, Freeman knew it was a suicide mission and he likely wouldn't be returning. Still, he made the journey, killing swaths of the Nihilanth's forces and finally the Nihilanth itself before being put in stasis by the G-Man.
When he arrived in City 17 years later, he learned of the Combine’s occupation of Earth and of the Resistance led by his old friends from Black Mesa. He joined the fight against the Combine, wanting the people of Earth to be free of the oppressive Combine rule, eventually becoming its de facto leader.
His actions make him out to be someone who values freedom for the common people and the oppressed, and someone willing to sacrifice his own safety for that of others, no matter the risk.

"Here, take this medkit!"
Freeman would primarily use Stimpaks (including Super Stimpaks and their Auto-inject variants) to keep himself alive, as well as Med-X to numb pain from the damage he sustains. If available, he may consume Ant Nectar from dead giant ants, much like the larval pellets seen in Episode 2, as well as Antivenom to counter any venoms he is exposed to.

Run. Think. Shoot. Live.
Freeman had zero combat experience or weapons training prior to his Hazard Course training. Despite this, he can efficiently use just about any weapons he gets his hands on, from a simple pistol to experimental energy weapons.
When in combat, Freeman takes a careful and considerate approach, calculating every shot he takes to ensure maximum effectiveness. However, he is prone to being caught off-guard, which may result in the enemy gaining an upper hand on him. Despite this, Freeman can spring back and get himself back together quickly.

Although Freeman travels on his own for most of the series, he is occasionally lucky enough to have someone by his side, whether it be a scientist or security officer he asked to follow him, Alyx or Barney watching his back in City 17, or a party of rebels whom he could command. Despite his silent and solitary nature, Freeman may occasionally accept help from a companion if the situation calls for it.

• Arcade Gannon
  
  Being a fellow scientist, Gordon respects Arcade. His witty banter would prove a nice contrast to Freeman’s silence, and he would appreciate Arcade’s views on an independent Mojave. Given Freeman’s low Speech skill and high Intelligence, however, he would need to either take Confirmed Bachelor or gain reputation with the Followers in order to recruit him. He would want Arcade to stay at Freeside during the Second Battle of Hoover Dam in order to stay safe and provide help to the locals in Freeside.
  
  
• Craig Boone
  
  Freeman would appreciate Boone’s sharpshooting skills and quiet demeanor. His troubled past at Bitter Springs might upset Gordon, given his own experience with soldiers “following orders”, but he would want Boone to repent and hopefully heal.
  
  
• Lily Bowen
  
  Despite being a Nightkin, Freeman would empathize with her, having seen a similar experience to hers among the Vortigaunts. After seeing the symptoms of her schizophrenia, Freeman would likely convince her to take her medicine regularly.
  
  
• Raul Tejada
  
  Gordon would appreciate Raul’s sarcasm and humor, similar to that of Barney. Although he greatly admires Raul's vaquero past, Gordon might encourage him to settle down as a mechanic.
  
  
• Rose of Sharon Cassidy
  
  Gordon would likely be unable to recruit Cass due to his low Speech and Barter skills. However, he would still find her no-nonsense attitude a little intimidating, but respectable.
  
  
• Veronica Santangelo
  
  Veronica’s engineering skills and sense of humor are reminiscent of Alyx, and something Gordon finds useful and charming. Her tendency to question authority would resonate with him, despite her loyalty to the Brotherhood. Gordon would want her to leave the dying Brotherhood to pursue her own goals.
  
  
• ED-E
  
  Much like Alyx’s D0G, Gordon would find ED-E to be a valuable robot asset. When prompted to have ED-E upgraded by either the Brotherhood or the Followers, Gordon would likely prefer the Followers.
  
  
• Rex
  
  Also like D0G, Rex is a loyal canine-robot companion. When giving him a new brain, Gordon would probably prefer to increase his damage output with Rey’s brain or damage threshold with Lupa’s, but Violetta is still a viable choice.

• NCR
  
  Although Gordon understands the desire to return to the way the world once was, he would see their bureaucracy, past crimes (such as Bitter Springs), and corruption as a hindrance to governing the Mojave. He’s unlikely to do anything that would put him on their bad side anyway, but he wouldn’t want to actively assist them if he didn’t think it would benefit the wider Mojave.
  
  
• Caesar’s Legion
  
  Even before meeting them, the stories told of the Legion’s slavery and cruelty would immediately set off alarm bells for Gordon. This is only vindicated after meeting them, as an entire nation built on enslaving people and sentencing criminals to cruel fates is quite reminiscent of the Combine. He would want nothing to do with them.
  
  
• Free Economic Zone of New Vegas
  
  Freeman would want the people of Vegas to be free of any tyranny. Although House, much like the G-Man, could manipulate him into doing his dirty work, Freeman might soon realize he’s no less of a tyrant than the NCR or Legion.
  
  
• Boomers
  
  Despite their reclusive nature and hostility to outsiders, Freeman would understand that the Boomers’ solitude and defense has allowed them to thrive. He would want their immense firepower on his side and potentially encourage them to venture out of Nellis to use their power to support the rest of the Mojave.
  
  
• Brotherhood of Steel
  
  Although their wealth of technology would prove incredibly useful to the Mojave, their hoarding of it and hostility to outsiders with their own technology would force Freeman to take them out of the picture.
  
  Followers of the Apocalypse
  
  As a fellow doctor, Freeman would admire the Followers’ dedication to helping the people of Freeside and greater Vegas, and would even help them out, eventually recruiting them to provide aid to New Vegas after the Second Battle of Hoover Dam.
  
  
• Great Khans
  
  Despite their brutal ways (and their role in his shooting), Freeman would sympathize with the Khans after learning of the their history and brutal treatment by the NCR. Freeman would encourage Papa Khan to break the Khans’ alliance with the Legion and claim their legacy in the Northwest.
  
  
• Powder Gangers
  
  Freeman would detest the convicts’ treatments of the citizens of Goodsprings, Primm, and the rest of the Mojave.
  
  
• White Glove Society
  
  Freeman would find the White Gloves’ wealth and mystique intriguing, but would be turned off by their cannibalistic nature upon learning of it.

"Tell me, Dr. Freeman, if you can. You have destroyed so much. What is it, exactly, that you have created? Can you name even one thing? I thought not."

The way I see it, there are two possible endings for Gordon:

1. Mr. House manages to keep him under his control: Freeman becomes a pawn, performing House's dirty work just as he did for the G-Man---delivering goods and items, meeting allies and enemies alike, recruiting and/or destroying said allies and enemies, and whatever other duties House needs done. The people of Vegas may be "free," but Freeman is not.
   
2. Freeman breaks away from House: Freeman realizes he doesn't need to be another piece on the chessboard and takes House's power away, installing Yes Man (and thus himself) as de facto leader of New Vegas. Freeman would want to ensure the formerly downtrodden citizens of Freeside, Outer Vegas, and the greater Mojave are able to live free of authoritarian rule, and possibly even simpler lives reminiscent of the pre-War days.

I hope this guide was a good read! It's my first time writing one, and figuring out formatting was a bit of a nightmare. Let me know what you think! If enough people like this one, I might make more for other characters in the Half-Life series or other Valve IPs (or just other stuff I'm interested in)!