the great mighty poo - conkers bad fur day.. just because its a giant singing poo
Deus from Xenogears its basically god and before you can fight him you have to kill its messengers.
final boss from marvel vs capcom. cant remember the name
final boss from guardian heros. cant remember the name either but it was freaking epic.
mother brain from super metroid... that was easy... oh wait... still kinda easy but its fun.
zakraid from i wanna be the guy.. a cross between zangief and kraid... best idea ever.
http://www.youtube.com/watch?v=5KTa7ra8M1o
dancing whore - parodius 3 or whatever its called.
final boss from ff iv
satan like thing from exhumed
pretty much all of the bosses from the old school goemon, castlevania and contra games.