CHEATCODES

Hit F2while playing to bring up the console window and type any of the following codes:

maxammo Full ammo for equipped weapon.
healme [#] Restore health to # entered, with 100 being the maximum.
superdeform Give enemies big head and feet on tiny bodies.
flowerpower 1 Changes blood effects to flowers.
playersonly You are the only one who can move. Doors become locked.
suicide Kill yourself.
quit End game.

TWEAKING

CHANGE RESOLUTION
XIII.INI

On your XIII installation folder, look for a folder called system
Inside it, you will find a file called XIII.ini
Open the file with Notepad and find the lines FullscreenViewportX=and FullscreenViewportY=
Change the values to your desired resolution, like 1920x1080.