Silent sniper bullets
Enter Stealth as a profile name.
Exploding rats
Enter Ratbomb as a profile name. Shoot rats to make them explode.
Hints
Secret mission
Successfully complete the game under any difficulty setting.
Third person view
Hold [R2] until the camera icon appears in the top right corner. Press [Up] or [Down] to zoom the view in and out.
Easy kills
Walk around with your machine gun to easily kill opponents in close combat. However, if you see a sniper at a distance, press [R3] to quickly use your sniper rifle.