Animal Crossing!!!

It's an awesome game. I've already got my house built up to it's maximum.

Bob, if you liked The Sims (or really any of the Sim games) you'll love this. The best description I've heard for it is "This game is everytning The Sims failed to do, only done right." It's obnoxiously cute, but very entertaining.

As far as accessories go, you can link the GBA to it, and you can use the E-Reader with it.

If you want more suggestions for GameCube games, buy Super Mario Sunshine, Resident Evil, Eternal Darkness, or Star Fox Adventures. All of them are badass beyond words.