Anything and everything Rare made for the system - Banjo Kazooie, Tooie, Perfect Dark, Jet Force Gemini, Killer Instinct, Donkey Kong 64, etc. I'd also check out stuff like Turok and if you're going obscure, look into Snowboard Kids. Super Mario 64 is a must, as well as the Zeldas. F-Zero was fun, but the gamecube version was better in my opinion - same for Wave Race. Also, if you like flying games at all Pilotwings 64 was just a lovely lovely game. Also, get yourself Rogue Squadron and Shadows of the Empire if you like original trilogy Star Wars. Hell, even Battle for Naboo is a pretty solid game considering the weak source material.
I'd make Pilotwings a priority though. I wanna play that right now, come to think of it.