Gamecube has some nice horsepower behind it only problem is that because the system is over run by so many crappy licensed games there are very few games that show off what the GC is really capable of. Here's a brief list of games the show of the GC hardware best.

Rogue Squadron II
Resident Evil 4
Metroid Prime 1+2
Wind Waker
Star Fox Adventures

Err off the top of my head that's all I can think off all I'm sure there's at least one or two more. Oh I can't foget about the new zelda: Twilight Princess.