Cheats
To activate cheat enter the following at the Main Menu screen, you will hear a sound when cheat is activated and the cheat menu in the options will now be available:

All Weapons	Left Trigger, Left Trigger, X, Y, Y, Right Trigger, Right Trigger
Immunity	X, Y, Right Trigger, Right Trigger, Left Trigger, Left Trigger, Y
Invincibility	X, Y, Left Trigger, Right Trigger, Left Trigger, Right Trigger, Right Trigger
Unlimited Ammo	R,R,L,L,X,Y,Y
Unlock all Missions	X, X, Y, Y, Right Trigger, Right Trigger, Left Trigger
Unlock all Vehicles	X, X, Y, Y, Left Trigger, Right Trigger, Left Trigger