Some people don't like boss battles, I love them. My favorites must be the metroid prime battles, they are BIG and intimidating. When you first enter the arena you have the 'no way I can do this' feeling, then that feeling is comfirmed, and then after trial and error and countless deaths you finally beat them. The satisfaction of seeing those bastards finally crumble is hard to describe.

honourable mention: Serious Sam. That thing was HUGE

could have been: Zelda: the windwaker, they look cool, but are way too easy, much like the rest of the game.

I heard Painkiller has some pretty awesome bosses as well, this game shall be mine soon.