All bosses from Cave Story including the few optional bosses. Throughout the whole video only the pistol and machine gun were used as weapons. Also for those of you that haven't played this game yet: go do so.

Timestamps:

Balrog (First fight) 0:03
Igor 2:06
Balrog (Second fight) 2:50
Balrog (Third fight) 4:00
Curly Brace 6:38
Omega 8:01
Rabid Toroko 8:47
Puu Black 11:10
Monster X 11:52
Balrog (Fourth fight) 13:55
The Core 16:05
Ironhead 18:26
The Sisters 19:26
Ma Pignon 20:43
Red Ogre 22:13
Misery 22:47
The Doctor 24:09
Undead Core 26:04
Heavy Press 30:41
Ballos 31:28