While  in  game  press  "Enter"  and type "<cheat> " (include the
space  after  <cheat>),  followed with the one of the codes from below
and then press "Enter" to enable the code.

mpcanthurtme        God mode on/off 
mpschuckit          Add weapons and ammo 
mpsmithy            Full armor 
mpkohler            Full ammo 
mpstockpile         Full ammo (maybe with differences?) 
mpbeamme            Beam player to level start with initial conditions 
mpsixthsense        No clip on/off
mpicu               3rd person mode on/off (HUD doesn't visible in this mode) 
mptachometer        Show speed info on/off 
mpsizeme            Show size info on/off
mpgrs               Show rotation info on/off
mpgps               Show position info on/off
mpfov               Edit (with keys) FOV value
mpvertextint        Edit (with keys) vertext tint
mplightadd          Edit (with keys) light amplification
mplightscale        Edit (with keys) light scale
mpbreach            Edit (with keys) weapon breach
mpwmpos             Edit (with keys) weapon offset 1
mpwpos              Edit (with keys) weapon offset 2