Mario 64, Perfect Dark, Banjo-Kazooie, Conquer's Bad Fur Day, Starfox 64, Mario Party, Pokémon Snap. The problem is most games have a GC sequel that was a massive improvement, like Super Smash Bros and Mario Kart, or they were dogshit but I was too young to know better. I end up playing more SNES games on my handheld emulator system because they couldn't improve 2D games after 3D was doable.

Absolute musts are Zelda: Ocarina of Time and Zelda: Majora's Mask. Otherwise stick with the rest of the popular ones and you'll be alright - Mario 64, Donkey Kong 64. Star Wars had a few good ones - Rogue Squadron, Shadows of the Empire (janky as fuck, probably didn't age all that well, but was pretty innovative for its time), Episode 1 Racer (although if you're also emulating PS2 games, Star Wars Racer Revenge is much better imo).

Jetforce Gemini ofc, but I'm not kidding about the controls being dogshit - proceed only if you're willing to completely rewire your perception of which buttons are supposed to perform which actions.

Some multiplayer greats are Super Smash Bros and Gauntlet Dark Legacy.

IIRC Aero Gauge was a decent racer, although the SW ones are better.

Kirby Crystal Shards was a solid 64 adaptation.

...I think at this point I'm just rattling off what I can remember from my own collection, lol. The nostalgia juices are really flowing!

The other comments have good suggestions, but I'll Add Rogue Squadron. Ogre Battle 64 is also good if you like strategy RPGs.

Dude you have to get ship of harkinian if you never played oot

Duke Nukem and obviously Golden eye were our two favorite PvP shooting games on the N64... not sure I'd recommend it for the single player tho