Enter the following console commands:
Toggle God mode: playbetter
All items: suckitdown all
Level select: changelevel
Toggle targeting: aquaticape
Toggle no clipping: kiwi
Kills all monsters in level: victor
Kill all non-Boss monsters in level: meatwagon
Display coordinates: showcoords
Select previous weapon: weapprev
Select next weapon: weapnext
Chicken mode: suckitdown chicken
Aggressive monsters: angermonsters
Bezerk monsters: crazymonsters