At the start of the level where you must catch Casey Weber, you will have to find a man who tells you where Casey is located. After he tells you, keep on shooting him and your points will keep increasing. This man does not die. To save your bullets, just punch him or enable the "Cheat mode" code.
Pause the game during the Afghanistan-Pakistan Border mission, then press Circle(3), Square(3). Enemies will randomly appear as Osama Bin Laden. Note: They will still be normal in every way except appearance, and will not be a Boss opponent.
At the title screen, press Circle(5), Square(4). If you entered the code correctly, you will hear a sound. Select the "Special Features" option to access the cheats, which can now be enabled individually before starting a game. The cheat options include "Invincibility", "Infinite Ammo", "All Fugitives", and "All Weapons".