Pause the game, hold the left trigger + right trigger and press down, a, x, black, a. You can now enter the following:

 Disable Shellshock – Press X, Y, A, B, Left, Trigger, X.

Infinite Health – Press white, black, Y, white, Left trigger, left trigger.

Hide Hud – Press black, left trigger, black, right trigger, up, Y.

Kill Nemesis – Press right, left, right trigger, left trigger, X, Y.

Unlimited Ammo – Press, L, Y, B, up, A, A.

Faster Vehicles – At the main menu, hold L + R and press X, X, Y, Y.

1-Hit Ko – At the main menu, hold L + R and press A, X, X, A.

Disable Hud – At the main menu, hold L + R and press A, B, Y, X.

Chicken Heads – At the main menu, hold L + R and press A, X, X, B.

Japanese Crash – At the main menu, hold L + R and press B, X, B, X.

Drive A Block Vehicle – At the main menu, hold L + R and press X, X, Y, B.