Goldeneye. First 64 game I ever owned. Nothing like playing through the entire game on Agent, then coming back years later, an experienced FPS man, and skipping to play it on 00 Agent! Playing Unlimited kills (translation, end at 100 kills) on Stack/Library with Power Weapons or Proximity Mines. I was always the Arctic Commando, then moved on to Civilian #3. RCP-90s and Assault Rifles abound.
Legend of Zelda, OoT. Took me several years to beat that game - was forced to buy it instead of Perfect Dark. Eventually my mind matured enough to find the Shadow Temple and the Spirit Temple (my older brother had done the Water Temple for me, it would take a replay for me to discover the horror) and I did trump them. Ganondorf was tough but so great to win!
Starfox64 or Lylat Wars as well call it. Incredible fun - I still play it today! The medals on Zonness, Aquas and Titania continue to allude me. I will get them someday!
Legend of Zelda, Majora's Mask. In my opinion, the best Zelda game ever. It was so dark and perfected compared to OoT, which was epic but felt empty much of the time. Beating all of the bosses with Chateau Milk and then stepping up to Majora was incredible. Shame he was so easy.
Pokémon Stadium and Mario Party 2, two games with minigames that we still play today. Clefairy Says, Magikarp Splash, Lickitung and his sushi... Brilliant. In Mario Party, we aren't fans of the actual main gametype but playing the minigames with 4 people is great fun. Favourite games are Hexagon Heat and Honeycomb Havoc... Shock Drop 'n' Roll is great too!
MarioKart64 was incredible. Playing as Yoshi and trumping all of your friends on Rainbow Road is on of the best feelings ever...
...I gotta dust off my Ninty!