Cheat Mode:
Press Return and type in "I_Wanna_Cheat." Then hold the Left Shift and 0 on the
Keypad and press Return at the same time. Now press Return, type in the cheat and
Return again. 

Here are the cheats you can type in after pressing Return once:

ARMAGEDDON              Meteor Shower 
EAGLE_EYE               See All 
EINSTEIN 1              Fast Explore On (0 For Off)
EINSTEIN 0              Disable fast exploration   
HASTA_LA_VISTA_ENEMIGOS Destroy All Visible Units and Objects 
I_HATE_LIMITS #         Set Unit Limit to # CR 
I_LOVE_THIS_GAME #      Give # of CR 
NO_MORE_SECRETS         Full Map 
NO_ONE_HIDES            See All Units 
SEE_YOU_NEXT_LIFE       Destroy Selected Unit 
THE_HAMMER_OF_THOR      Kill All Enemies At Range Of 8
MASSACRE                Destroy all objects at range of 8 
X-MAS_PACK              Full Repair And Reload Ammo
ONE MORE PLEASE (x,y chassis number weapon) Create object or building at indicated coordinates    
TIME IS RELATIVE        Faster research   
DIRT CHEAP RESEARCH     Cheaper research
LET BE DARKNESS         Fog
BAD TIME BAD PLACE      Damage all nearby units
HELP ME PLEASE 1        Enable fast exploration, player only   
HELP ME PLEASE 0        Disable fast exploration, player only