Super Monkey Ball was the game that I got with my Gamecube, I had so much fun with it between the main game and the party games, especially monkey target. I've purchased several of the sequels but none of them have quite matched the magic of the first game.
I never played the first Pikmin on Gamecube (but I'm working on playing through it now on Wii) but I picked up the second one and had a blast with it. Such a brilliant idea for a game and also so frustrating that Wii never got an entry in the series, and neither did the DS, which I thought would be a good fit for the series with the touch screen controls.
Mario Sunshine just didn't do it for me, I tried hard to get into the game on more than one occasion but just couldn't. I loved Mario 64 and I loved the Galaxy games but I just couldn't get into Sunshine. Maybe I need to give it one more try one of these days.
Animal Crossing was a blast, I was seriously addicted to that game for a good year or so, I remember waking up early before school to play (collecting mushrooms maybe) which was insane considering I'm anything but a morning person. The characters, the holidays, the change of seasons, the collecting aspect were all brilliant. And the NES games being included was such a great bonus, I played so much Wario's Woods in particular. The first year it was out I was over at a friend's house and there were 2 or 3 of us all in our Animal Crossing towns for New Years. I never played the DS or Wii versions since reviews all said they were basically the game. I'm thinking that I might pick of the Wii version since it's on sale for $15 on Black Friday.