When spotting an enemy:
敵歩兵発見！: teki hohei hakken! : Enemy footsoldier spotted!
アメ公がいます！: ame-kou ga imasu! : Yankee over there!*
向こうに敵歩兵！: mukou ni teki hohei! : Enemy footsoldier ahead!

When under fire:
攻撃されているぞ！: kougeki sareteiru zo! : We're being attacked!
援護を、頼む！: engo o, tanomu! : backup/support/cover, please!
どこからくるんや？ : doko kara kurun ya? : Where'sat comin' from? (Kansai accent)
敵が見えへん！ : teki ga miehen! : I can't see the enemy! (Also Kansai accent)
このままじゃ全滅するぞ! : kono mama ja zenmetsu suru zo! : They'll annihilate us if this keeps up!

Suppressing an enemy:
敵が恐れているぞ！: teki ga osoreteiru zo! : The enemy is frightened!

Under fire by artillery:
来るぞ！ : kuru zo! : [it's] coming!
砲撃！ : hougeki! : artillery!
Officer/commander under fire:
お前ら、反撃しろ！ : omaera, hangeki shiro! : Counterattack, you lot!

When wounded:
くそ、やられた! : kuso, yarareta! : ♥♥♥♥, I'm hit!**
くそ、やれやがったな！: kuso, yareyagatta na! : ♥♥♥♥, he ♥♥♥♥♥♥' hit me!**
ちっくしょ、やられた！ : chikkusho, yarareta! : Crap, I'm hit!

Bleeding out:
母。。さん。。。 : kaa..san... : momma...
なぜ俺が。。。 : naze ore ga... : Why me....

Banzai charging:
天皇陛下万歳！: ten'nou heika banzai! : Garners no explanation. Literally, "ten thousand years of life to His Majesty the Emperor!"
殺せえええ！ : koroseeeee! : Kill theeeem!
ああああああああ！ : aaaaaaaa! : aaaaaaah!

When depleted stamina:
ちょっと待っててくれ。 : chotto mattete kure : Wait a bit.
ちょっと休ませてくれ : chotto yasumasete kure : Let me rest a bit.
先に行け！: saki ni ike! : Go on ahead!

Reloading:
弾が入っているぞ！: tama ga haitteiru zo! : Reloading!***
もう、弾が足りない！ : mou, tama ga tarinai! : I don't have enough ammo!

Misc:
陛下のお為に、攻撃！ : heika no o-tame ni, kougeki! : For the honorable sake of His Majesty, attack!
陛下のお為に、走れ！ : heika no o-tame ni, hashire! : '' '', retreat/run!
おい、そいつ味方ぞ！　撃つのを止めろ！: oi, soitsu mikata zo! utsu no o yamero! : Oi, he is an ally! Stop shooting!
何やってんだ！？ : nani yattenda!? : What the hell are you doing!?
仲間がやられた！ : nakama ga yarareta! : A friendly has been hit!
尻尾巻いて帰れ！: shippo maite kaere! : Turn tail and go home!
主管どの！何すればいいですか？　shukan-dono! nani sureba ii desu ka? : TL! What should we do?
まだ戦える！ : mada tatakaeru！ : I can still fight!

TL radio interactions:
もしもし、こちら小隊長から大隊隊へ。偵察機を要請します。　どうぞ！
moshimoshi, kochira shou-taichou kara daitaichou e. teisatsuki o yousei shimasu. douzo!
Hello, platoon commander to battalion commander. Requesting reconnaisance plane. Please go ahead!

もしもし、こちら小隊長から大隊隊へ。砲撃を要請します。　砲撃を。。
moshimoshi, kochira shou-taichou kara daitaichou e. hougeki o yousei shimasu. hougeki wo...
Hello, platoon commander to battalion commander. Requesting artillery attack. Artillery on...[coordinates]

Pre-match peptalk:
我々は大日本帝国の軍人である！必ず勝つ！
wareware wa dai nippon teikoku no gunjin de aru! kanarazu katsu!
We are soldiers of the great empire of Japan! We will assuredly win!

These are words that are often shouted individually, or as a nonvariant part of randomly said phrases, are useful to know or I just couldn't remember the whole phrase.

手榴弾 : shuryuudan [or] teryuudan : grenade (when you hear this, move!)
砲撃 : hougeki : artillery
機関銃 : kikanjuu : machine gun
火炎放射器 : kaen-houshaki : flamethrower
歩兵 : hohei : footsoldier
工兵 : kouhei : combat engineer
狙撃手 : sogeki-shu : sniper
銃撃 : juugeki : gunfire
突撃 : totsugeki : charge, assault
敵 : teki : enemy

* Ame-kou is a slur used against Americans, I had to look this one up. -kou was originally an honorific title for someone with a court rank of a duke. In a weird process which is surprisingly common in Japanese it went from honorific to a slur, also used in words like ポリ公[pori-kou], "cop"
** "kuso" literally means "feces", but is a much milder expletive in Japanese than the equivalent word in English, on a level more similar to "damn". "yagaru" is a suffixal verb which shows contempt or disdain for the action it is suffixed to. Possibly comes from the verb "iyagaru", to hate/dislike. Not technically an obscenity but difficult to translate into English without one.
*** Literally "inserting rounds/bullets/ammunition!"