Add the set developer 1 set svcheats 1 command line parameter. Press during game play to bring down the console window.
Spawn item: give item
Full health: give health
Save game: savegame
Load saved game: loadgame
Get all items: give all
Ammunition: give ammo
Invincibility: god
Ignored by enemy: notarget
No clipping: noclip
Fly mode: ufo
Teleport to a specific map node: jumptonode
Play indicated map: map map name
Suicide: kill