Wario Ware: Smooth Moves is an amazing game for local play. It is everything the Wii promised itself to be. Fun, different, a good way to see your friends look stupid, and a great party game. The GameCube Wario Ware is also pretty amazing if you have enough GC controllers.
Dokapon Kingdom is a blast as well. It has to be one of the most fun ways to lose a friend. The game specializes in you screwing over every other "hero" in a race to save the world! Mix of Final Fantasy and Monopoly. Well really more like Munchkin the board game, but I assume you never played Munchkin.
It is hard to go wrong with Mario Party too. Same concept, but not as fun as Dokapon if ya ask me.
de Blob is the only other game I could highly recommend off the top of my head. It is like a 3D platformer, but it plays very differently. The game is essentially an interactive coloring book. It is really well done though, and easy to find on the cheap at this point.
Word of warning on Wario Land. It is massively over hyped on these forums. It is a decent enough 2D platformer, but nothing to write home about. Not even my combined love of 2D gaming, and 2D platformers could convince me to do more than rent the game.