On the main menu, go into Police HQ, then Cheats to activate and deactivate unlocked cheats. It seems that one gets unlocked each time you beat the game. -- Decapitation - Headshots decapitate enemies. -- Infinite Grenades -- No Reloads -- Molotovs - Grenades turn into Molotovs. -- Infinite Ammo -- Walking Enemies (Non-Sniper Levels) - Enemies walk, don't run. Doesn't work in sniper levels because if everyone walked in them then the stages would take AGES to finish. -- Extreme Gore - Makes enemies bleed, leaves blood stains on the ground, but not really Extreme. -- Drug Effect - Crappy motion blur effect, which goes away if there's lot of enemies or buildings in the background. -- Super Shotgun - A slightly more powerful shotgun blast which knocks the enemy back. -- Exploding Enemies - Kill an enemy and it goes boom! If you kill them while they're close to you, you'll take damage.