God Mode
Since XIII is running off a varient of the Unreal engine, you simply need to add a keymap to the GOD cheat code.

WARNING: This requires editing .ini files. Be sure to backup any files you edit.

Go to your XIIISystem folder (i.e. C:Program FilesUbi SoftXIIISystem for the standard install.) Open up user.ini in notepad.

Find:

Comma=

and replace it with

Comma=GOD

Save the file and then run the game. Pressing the Comma (,) key will turn on god mode. This should work on both the demo version and the retail version.

Cheat Codes
While playing, press F2 to bring up the input box, type any of the following cheat codes then press [ENTER]:

Code - Effect

maxammo - Max Ammo
healme # - Add Health (# is a number 1-100)

Quick gun
At the start of the game, run though the back door to a gun faster and safer than going to the man at the front. Note: Hit him in the head and he will die faster.

Better sniping accuracy
When in sniper mode, zoom in. To steady yourself for greater accuracy, sit there and do not touch anything to look or move for about five secounds or until he stops moving around. You can now look around with perfect dead aim accuracy.

More ammunition
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.

Ubisoft logo
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.