originally posted by ServiusTheBear
Make sure the Developer Console is enabled in options, and assign a proper key to open the console. Open the developer console in-game and note the following commands:
God - Makes you immortal (Your health is static)
noclip - Ability to fly, even through walls (Type again to toggle)
ent_create_portal_companion_cube - Creates a Companion Cube
ent_create_portal_reflector_cube - Creates a Reflector Cube (For lasers)
These are just a few that I have tried and that work. Slight warning it will disable achievements and stats. Also remember to type sv_cheats 1 first.
"ent_create_portal_companion_cube" & "ent_create_portal_reflector_cube" don'tr need sv_cheats 1. Nor do any of the other "sv_" or "ent_" codes. These can still be used to get achievements.