Cheat mode:

Make a backup copy of the file before proceeding. Use a text editor to edit the "armyops.ini" file in the "system" folder in the game directory. Add the following line under the "[Engine.GameEngine]" heading to enable cheat mode.
bMPCheats=Enabled 2

Then, press ~ or [Tab] during game play to display the console window:
Result - Code:
Third person view - behindview 1
Unlimited ammunition - mpcheat paramsammo 1
No clipping mode - mpcheat ghost
Disable no clipping mode - walk
Weapon select mpcheat - changeclass [weapon name]
Start game alone - start [level name]
Freeze game play - playersonly