Hey Guys.
I am looking for some good GameCube games with coop mode. You know some?

Final Fantasy Crystal Chronicles
Zelda 4 Sword Adventure
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Also see
http://www.mobygames.com/attribute/sheet/attributeId,619/p,14/

Tell me when I am wrong, but i think for those games you need a Gameboy Advance for every player... My budget says: no
So I need games you can play with the Cube controller.

The Conflict Desert Storm games were some excellent co-op fun on GC, I highly recommend them. Mario Kart Double Dash's single kart mode is awesome, you really have to work together. And erm... Rebel Strike, you can play a large chunk of missions in co-op. Hope that helps.

If you like action/RPG's you can't go wrong with Tales of Symphonia. The four-player battling in the game is just a lot of fun, so long as you have somebody willing to be Raine Sage (the healer).

If you have a Japanese GC (or modded North American one with a toggle to switch between NA/JPN then Mr. Driller Drill Land is your man! Godzilla Destroy All Monsters Melee is also pretty fun, though Unleashed for the Wii is better all the way around.

Lego Star Wars.

Also, the not great 'Star Wars Rogue Squadron 3' includes a co-op 2 player version of the much better 'Rogue Squadron 2' as an extra bonus (whoops, just noticed that was mentioned above - still it is cool). Also has all three classic arcade games as unlock-ables if you are into all things retro...