Cheat: Unlimited Ammo

Enter up, down, left, right, triangle, up, down, left, right, square during the game's intro movie.

Cheat: Double Your Health.

Enter up, up, left, left, right, right, circle, circle, down during the game's intro movie.

Cheat: Unlockable Characters

To unlock Yuri Complete 'Jimmer Collins' level
To unlock Viktor Complete 'Beginning Of The End' level
To unlock Mahl Complete 'Your man with the tatoo' level

Cheat: Unlock Everything

If you beat the game you'll unlock all the bonus features, including all the characters and a Making Of video.