For me it's 'Fuzion Frenzy' and 'Bomberman Jetters'.
I'm pretty sure I've played those more than any other 3+ player simultaneous offline game that wasn't a 'Mario Kart' or 'Golden Eye' (or course)
Playing 'Fusion Frenzy' (with the DDR 4th Mix Soundtrack) was our freakin' life for like two years straight. It would have justified owning an XBOX if we never had another game for it.
Man, I really miss bring able to use your own custom soundtracks to games.