Press [Enter] then type code and press [Enter] again to activate:

Code - Result:
$WIN - Win Mission
$RU x - Give x Resource Units
$SU x - Give x Support Units
$GET TECH - Research All Current Techs
$GET ALL TECHS - Research All Techs
$FOGOWAR ON - Fog of War ON
$FOGOWAR OFF - Fog of War OFF
$GOD ON - No Effect?
$GOD OFF - No Effect?
$REPAIR ALL - Crashes Game
$WEAKEN ENEMY - Lower Enemy Hulls