Headhunter

Door password:

To unlock the room on the second floor of the bikers' hideout, enter "1993" as a password.

Kill Silently:

In some levels You do not want to attract attention so choose the Shield Pellets as a weapon and either throw one or don’t but walk up to the enemy and press L1+x and you will break there necks.

However, you have to get really close to them.

 

Debug Mode:

HOLD R1 + Square and press Start while playing the game.

All weapons and infinite ammunition:

You need to go to the Star Locker and open it. You can do this by breaking Hank Redwood's records in Leila mode, and completing the game.

However if you use the Star Locker you may not be able to complete the game afterwards