Enter these codes in the passcode screen.
BUTTERFLY - Unlocks All Missions
TANG - "Bullet Shield" mode
GOBY - Unlimitied Ammunition
MANDARIN - "Achilles Head Mode"
PUFFER - "Always Sniper" mode
TRIGGER - "Invisible Soldiers" mode
HOGFISH - "Perfectionist" mode
DAMSEL - "Rubber Grenades" mode
GARIBALDI - All Replay Items
SPINEFOOT - Makes Everyone's Arms Huge
SEAHORSE - Men With Hats
TILEFISH - Silver Bullet Mode