Liquid Snake (Metal Gear Solid 1) 2 Dudes fighting without shirt using their fists, what else can I say?
Gigantosaurus 2nd fight(Dino Crisis 2) It fought the T-Rex, a missile fell over it and still yet, the Giganotosaurus is still alive.
Vamp(Metal Gear Solid 4) This guy only dies if you inject him with syringe, so you can keep this exciting battle for as long as you want.
[spoiler:cfdbd87b18]Liquid Ocelot(Metal Gear Solid 4) MOST EPIC BOSS FIGHT TO EVER EXIST IN THE HISTORY OF HUMANITY[/spoiler:cfdbd87b18]
I liked Megaman X4 Bosses too. Hard as hell, beating them worthed a drink.
Tabuu(Super Smash Bros Brawl) Long and hard, that´s what makes it fun.
And Final Hazard.