XIII Cheats

In the ssh secret base at the third check point in the locker room
there is a secret vent where you are under a security camara  there is
a gi right in front of you so hurry

When you first start the FBI level, immediately after the woman shoots out your cuffs, go to the center of the room with the three computers. You will find the Ubisoft logo acting as a screensaver. Also, if you walk up to the computer screen, look down at it, and press A, the screen will say "GAME OVER".

More Ammunition:
If you wait until an enemy reloads his weapon and shoot him before he has a chance to fire it, you will get a full magazine for your weapon.

Click the Right Analog-stick to automatically center the crosshair at head height. This is useful on levels with lots of enemies and Xbox Live.

Wait until an enemy reloads his weapon before killing him. Kill him before he fires
his gun and you will get a full magazine for your weapon.