All Weapons:
Pause your game and quickly press Square, Circle, R1, L1, R1 + R2. If you completed the code
correctly Sarge will have access to all the weapons for the current level. 

Invincibility:
Pause your game and quickly press Square, Circle, L1, L1 + L2. If you completed the code
correctly Sarge will be invincible during the current level.

                             Game Shark Codes

     Infinite Health - 800432A0 2400 
     Infinite Ammo - 80057fd22400 
     Infinite Flamethrower Fuel - 80058e3e2400