Used to play N64 all the time at my friends house (which means my games are mostly all gonna be multiplayer.) I'd say my favorite games were:
1. Rush 2 - I'm not surprised if nobody remembers this one, it was just one of many racing games on the console, but we probably played it more than all the other games combined. Very combo-heavy and with a surpisingly advanced physics engine for its time. I remember each of my friends had a signature car, I always ran the taxi. When the N64 became obsolete this was the only game we'd still blow the dust off it to mess around on the stunt map some more.
2. GoldenEye - We played a ton of this as well, probably my earliest first-person shooter. But we completely dropped it after Battlefront I came out for the Xbox so I have far more memories of that game.
3. Super Smash Bros - Full disclosure, I was never a fan of this game, I pretty much just spammed Falcon Punch and got last place every round. But we did play a ton of it.
4. Mario Party - Yeah, like everyone else, we mostly played Nintendo games. I always played Luigi and (like in Smash) very rarely won. But I actually liked this game a lot
5. Star Fox 64 - Despite being singleplayer, we used to always pass the controller around every time someone died or completed a level. Lotta fun memories of this one, we used to think Slippy was a double-agent and intentionally kill him off since he and the villains both wore red caps with a single white letter. This was the first game that after we eventually beat it we looked-up walkthroughs on the internet to go find secrets and defeat the hidden bosses.