• All weapons -- RCKTSRDGLR
• Boat Assault bonus level in Campaign mode -- WRDRB
• Brandon's gang -- NNKNHCKS
• Invincibility -- HPPYHPPY
• Level select -- 8ODYS
• M2 Hydra Tank in multi-player mode -- TRDDYBRRKS

Weapon Power-up
Get 15 of some items and press the a,b and z buttons to make the weapon stronger.
Submitted by Dude