Wind waker: What Flagel said. Graphics aren't that bad, the game's amazing.
Resident evil 4:Great graphics, great gameplay, great action.
Mario Kart Double Dash: I loved it. One of the best games on the Cube IMO.
Eternal darkness: only released on gamecube, it think.
I really enjoyed it, it's a good game and weird!
you control different characters throughout different ages, solving puzzles and fighting skeletons and other creatures.
If you lose your sanity, the next room would be turned upside down for example.
It is no RE4, but if you can pick it up cheap...
Pikmin: only played the 1st, it's another good and weird game, you have to grow little flower-people, each flower has it's own special trick (blue can walk on/under water).
Exploring the land to retrieve broken parts of your crashed spaceship. the pikmins would then carry those parts back home. But it's a dangerous world. With things trying to eat the little pikmins.

Get the second one though, it has a multiplayer mode.