Most games have them - some more memorable than others. What are some of the best boss battles you've ever fought, and what made them stick out?
Metroid Prime from Metroid Prime :P Not only is getting to the final boss challenging but the boss fight itself is as well. It's a long fight that has you constantly moving and evading attacks. It also utilizes almost every powerup you obtain in the game: the first phase has you use all of your beams and the second has you use all of your visors. Plus, the music is cool too!
Metroid Prime is definitely up there. As is the combination quiz game show and final battle from Banjo-Kazooie, for me.
My favorite boss fights are when you have to fight with the controls of the earlier Resident Evil games. ... Seriously though, one of my favorites is Ganondorf in The Wind Waker. Had such a great build-up, and the fight was really fun. The ending of it was also a bit of a shocker, too.