Resident Evil 0 Cheat Codes for Gamecube

Unlock New Costumes
If you complete the game on Normal or Hard mode, you'll find the Closet Key in Rebecca's Inventory when you start a new game.

Unlock Leech Hunter Game
Beat the game on Easy, Normal, or Hard mode to unlock this mini-game.

Save time
Open the lid on your gamecube and the time will stop until you put the lid down. This way you can get a better final time