Enable the console window in the game options. Then, press ~ and enter one of the following codes at the console window to activate the corresponding cheat function.

Effect Code

Get all weapons: wuss
Toggle god mode: god
Toggle no clip: noclip
All weapons: give all
Spawn indicated item: give
Set health level: health <1-100>
First person view: cg_cameradist -45
Return to default view: cg_cameradist 128
Level select: map
Toggle frame rate display: fps <0 or 1>
Disable enemy AI: notarget