The game that I keep my N64 out for is Sin and Punishment (Tsumi to Batsu). The Child of God is a rail shooter. The game is lush, beautiful, gripping, and actually replayable. Keep yourlady away from this game because it will make her loins wet with desire, and make sure to bring a spare change of pants for yourself.
I thought I was just going to be playing another shooter - I wasn't expecting a new religion...
If you like Anime, and you like shooters, and you liked Vagrant Story's style of art, get Sin and Punishment and dust off the N64. It's worth every penny.
Other than that - and all things other than that are deeply overshadowed - you must get Bust a Move 2, one of the best versions of Puzzle Bobble on any system, also known as Puzzle Bobble EX on the MVS. Only difference is that the 3D intro is real on the N64 version.
Personally I loved Yoshi on the 64. It had a lot of character. It was cute, very easy, but worth my time, yeah.
Mischief Makers - solid platformer. Like Top Hunter, but very very Treasure. That is a good thing.
Needless to say ISS 98/ISS 2000 (is there a ISS2000? I heard there is...). I'll only play a few sports games. This series is one of them.
Mario Golf - even if you hate mario, it's a damn good golf game. I don't like mario, but I can deal with him in this game.
If Blaine were alive today he'd say Conker's Bad Fur Day...