MotorStorm Cheats:

Huge Heads

Hold down L1, L2, R1, R2, R3 (hold to the RIGHT), L3 (hold down LEFT).

Unlock All

At the main menu enter following Hold down L1, L2, R1 and R2, and push R3 (the right analog stick) upward. Then, press L3 (the left analog stick), and push it down while keeping it pressed.