I use a Trio-Linker, bought it off Lik-sang (well, Xander bought it for me as a present), I can hook up my GC, PS2 or DC controllers to my PC. I play all my N64 roms with my GC controller too, it's close to the N64 controller, but I find it a million times more comfortable.

...Also it supports Maracas, Dance Mats and Bongos but just plain "why?" on those.