Cheat Mode:

Start the game with the “-console” command line parameter. This is done in the

properties of the you desktop short cut to the game. Press ~ to bring up the console

window, then enter sv_cheats 1 before loading a game or level to enable

cheat mode. Enter one of the below codes.

Code          Result  
god           God mode   
noclip        No clipping mode   
notarget      Become invisible
impulse 101   All weapons    
sv_gravity    Set gravity; 800 is default.    
sv_accelerate Set jump distance; 10 is default     
skill    Set skill level; 1 is easiest    
map           Level select    

Level Names:
Use one of the following entries with the map  code. 
ba_canal1
ba_canal1b
ba_canal2
ba_canal3
ba_elevator
ba_hazard1
ba_hazard2
ba_hazard3
ba_hazard4
ba_hazard5
ba_hazard6
ba_maint
ba_outro
ba_power1
ba_power2
ba_security1
ba_security2
ba_teleport1
ba_teleport2
ba_tram1
ba_tram2
ba_tram3
ba_xen1
ba_xen2
ba_xen3
ba_xen4
ba_xen5
ba_xen6
ba_yard1
ba_yard2
ba_yard3
ba_yard3a
ba_yard3b
ba_yard4
ba_yard4a
ba_yard5
ba_yard5a 

Grunt-O-Matic:

In the console type in impulse 76 and then start a new game or load a game. Then

type it in the console again and then you can spawn lots of marines. [tip: be

careful, if you spawn one near a wall the model will get stuck in the wall and

your game will crash. Also type in notarget and you will be invisible to all enimies

so you can hang out and kill scientists and aliens with the marines.

Thanks to Revolution readers FFM Fry and AJ!