The mods below are the mods that i'm personally using when playing Oblivion.

My goal is to improve the game but by keeping it very "vanilla friendly".

I will update this guide if i find more mods that deserve to be here.
If you want to suggest mods in the comment section, don't hesitate ! But remember i'm looking for mods that are keeping the game authentic.

Download : https://www.nexusmods.com/oblivion/mods/48832
This mod makes items and spells displaying a bit smaller in inventory. It is also making the inventory and map larger, taking more screen space.
It really helps navigating through inventory and map while keeping the vanilla look and feel.

Download : https://www.nexusmods.com/oblivion/mods/10254
In the vanilla game a lot of spells are sharing the same icon. For exemple, health restoration and fatigue restoration have the same red hearth icon.
This mod is adding more icons so you can manage your spells more easily. It's also helping to know what spell the enemy casted on you. For exemple, the fatigue restoration spell will now have a green hearth icon instead of red.

Download : https://www.nexusmods.com/oblivion/mods/12859
In vanilla game, everytime you sell an item you will have to confirm it by clicking "OK" in the middle of the screen. It can be really tedious when selling a lot of items.
With this mod, if you're holding "SHIFT" while selling an item it will automaticaly confirm. If you're holding "CTRL", it will automaticaly sell just one item of the stack.

Download : https://www.nexusmods.com/oblivion/mods/23069
When you have a lot of spells, it may be difficult to navigate through and find the one you're looking for.
With this mod you will be able to remove spell from your inventory, so you can get rid of the low tier spells that you don't use anymore. To delete a spell, put your mouse over it in inventory, then press "DELETE" on your keyboard. A confirmation prompt will appears, asking if you really want to delete it.

Download : https://www.nexusmods.com/oblivion/mods/3409
This mod will hide all your keys in your inventory and display a single item called "Keychain" instead. Clicking on keychain will show all your keys again until you close your inventory. This mod will really clean your inventory !

Download : https://www.nexusmods.com/oblivion/mods/44337
Wow ! With this mod you can see your feet while in first person ! Must have !

Download : https://www.nexusmods.com/oblivion/mods/1840
In vanilla game, you will notice that your camera is drifting when playing on third person, making it very hard to control.
This mod fixes that, so the camera will finally follow your mouse movements.

Download : https://www.nexusmods.com/oblivion/mods/39322
In vanilla game you're increasing your magic skills by a fixed amount for every spell you cast, independently of the spell level. It means that the best way to train your magic skills is by casting a weak low mana cost spell over and over again. In my opinion, this is really stupid and tedious.
With this mod, your magic skills are increasing according to the quantity of mana that the spell cost. You can now increase your skills by playing normally and you don't have to spend hours casting spells in town to train it.
The mod may sound like cheating, but honestly that's how it should be in vanilla game.

Download : https://www.nexusmods.com/oblivion/mods/10947
In vanilla game you're increasing your marcantile skill by a fixed amount for every item you're selling, independently of the item value. You have to sell approximatively 25000 items to reach mercantile level 100. The best way to train it is by selling 25000 arrows one by one. Of course, this is really tedious and stupid.
With this mod your mercantile level will increases according to the value of the items sold. You can finally sell your items in batch and not one by one. No need to buy and sell arrows for hours, you just have to play normally.
The mod may sound like cheating, but again, that's how it should be in vanilla game !

Download : https://www.nexusmods.com/oblivion/mods/1843
This mod removes the ugly persistant glowing effect when using an enchanted armor. You still can see ephemeral glowing effects.

Download : https://www.nexusmods.com/oblivion/mods/11891
I usualy don't like graphical "improvement" mods, most of the time it's just killing the charm of the game and its artistic direction.
But this one really doesn't hurt. It's improving the detail quality of the trees and flora while remaining in the tone of the game.

Download : https://www.nexusmods.com/oblivion/mods/8011
This mod is tweaking water rendering settings to make it looks a bit better. This one doesn't hurt either.


Download : https://www.nexusmods.com/oblivion/mods/48808 (Removed from mod nexus)
For a long time i restrained myself to use this kind of mods, because i always found that it was changing the game too much.
But i decided to try this one, and i didn't regret it. This ENB is making everything looking smoother while keeping the natural tone of the game.
If you're going to install it, i recommend to disable "Depth Of Field", unless you like it when everything is blurry.

Download : https://www.nexusmods.com/oblivion/mods/5429
Tired of your character screaming like mad man every time you're doing a power attack ? This mod remove that.
For real, in vanilla game i was avoiding doing power attacks just because of how annoying those screams are.

Download : https://www.nexusmods.com/oblivion/mods/46155
This one is just a personal preference, but i don't like how my character looks when using a Daedric armor.
This mod is just replacing the skin of the Daedric armor set.

Download : https://www.nexusmods.com/oblivion/mods/43879
This mod is adding a lot of weapons to the game. The weapons can be found anywhere (merchants, chest, enemies, npc, etc...). The weapons added are trying to be balanced and well integrated in the world.
The mod is not perfect, some weapon are feeling out of place and does not fit really well with the game. Some weapons are too overpowered, in particular some staff.
But if you're not going to tryhard with OP weapons and you close your eyes when an ugly out of place weapon is on the screen, the mod will bring some nice fresh air.
There is really a lot of weapons in this mod and a lot of them are really well done and working very nicely with the game aesthetic.
It's pretty cool to change weapons from time to time when you find a cool looking blade or hammer. Give it a try if you're tired of always using the same boring top-tier weapon in your vanilla game.
I hesitated to put this mod in this list, because it's not really in the theme of "Essential mods for better vanilla style gameplay", but i had some great fun with this mod, so i had to share it.
Something i really liked doing with this mod is collecting every different weapon i found and displaying them in my house by carefuly hand placing them around. Looks like a real museum here :D