kill.switch

Level select:
Press A, B, Y, X.

Archer character:
Press R, Y, X, B.

Pistol:
Press X, B, Y, A.

Unlimited ammunition:
Press R, L, A, B.

Unlimited heath:
Press L, Y, R, B.

Level select:
Successfully complete the game under the normal or hard difficulty setting to unlock an option that will allow you to pick any level in the game.
Magicmomentsandu.

Hint: Grenades:
When on any level and there are two enemies talking to each other, throw a grenade (for example at the beginning of the Think Like A Gun level). They will not even look to see what it was because they will be distracted.
Magicmomentsandu.

Hint: Shooting enemies:
The best way to kill someone is to pull the trigger when your crosshairs are red.
joshua steele.

Hint: Shooting hidden enemies:
Some enemies hide in areas where you cannot shoot them. Throw a grenade at them and they will jump out of hiding. When they jump out, they will land on the ground on their stomachs. They will require a few seconds to get back up. Before they do, aim and shoot them or they will go back and hide again.
SVB1115.