When you are in gameplay press enter and type in <cheat>mpxfiles and then you will hear a sound of a predator mask that confirms that all the levels are anabled.

In single player mode press 'enter' then type, "<cheat>" then leave a space and enter one of the following codes:

For example to enable god mode, you would type the following:

"<cheat> mpcanthurtme" then press enter again.

mpcanthurtme= toggle god mode

mpschuckit= all weapons and ammunition

mpsmithy= full armor

mpkohler= full ammo

mpstockpile= full ammo

mpbeamme= beam player to level start with initial conditions

mpsixthsense= no clip on/off

mpicu= toggle third person mode

mptachometer= show speed info on/off

mpgrs= show rotation on/off

mpgps= show position on/off

mpsizeme= show size info on/off