Unlock Cheat Mode: At the Main menu hold Left + Square + L1 + R2 and the words 'Cheat Mode' will appear at the bottom of the screen if the code has been entered correctly. Go to the 'Options' screen and you will be able to unlock a stage select option and invincibility.
Unlock Extra Weapons: When you have completed a level and viewed the destruction bonus quickly move to the exit and if done correctly the screen will flash and you will hear a sound. When the next level begins a shotgun or handgun will appear. If the game is in 2-Player mode each player will receive either weapon.