Enter TEXAS as a code at the cheat menu. All weapons available in the current level will be unlocked.
Big Head Mode
Enter ''HEID'' as a code at that "Enter Cheat" screen.
Cheat Mode
Enter ''FMNFB'' as a code at that "Enter Cheat" screen to unlock all cheats.
Demo Mode
Enter ''HUNTER'' as a code at that "Enter Cheat" screen.
Float in air glitch
This glitch is a way to stay in the air forever. Choose multiplayer and choose any level where you can fall very far down, such as the treehouse level. Choose the start with all weapons cheat and play normally. Chose the gun that turns into that remote-control spider thing and jump off the treehouse. Don't stop pressing the jump button (A default) and you can move it around in the air and explore.
Invincibility
Enter EMERPUS as a code at the cheat menu.
Invisibility
Enter SLLEWGH as a code at the cheat menu.
Level select
Enter SELLOUT as a code at the cheat menu. Load a saved game and all levels will be unlocked.
Unlimited ammunition
Enter MADMAN as a code at the cheat menu.
Zoo Mode
Enter ''ZOO'' as a code at that "Enter Cheat" screen. This mode allows you to kill all animals.
All available weapons...