to enter the cheat console press enter and than type one 
of the following cheats:_

mpcanthurtme - Toggle invincibility
mpschuckit   - All weapons and ammo 
mpsmithy     - Full armor cheat  
mpstockpile  - Full ammunition 
mpbeamme     - Teleport to level start with default conditions 
mpsixthsense - Toggle no clipping 
mpicu        - Toggle third person view 
mptachometer - Toggle speed display 
mpsizeme     - Toggle size display 
mpicu        - Toggle third person view 
mptachometer - Toggle speed display 
mpsizeme     - Toggle size display