During gameplay, press "left shift" and "backspace" simultaneously.
This should result in a message "Debug mode now enabled!".

All these cheats can be entered as chat text. Enable debug mode, then press Enter, type the code, and press Enter again.
Some of them CAN, and WILL break the game. We can't stress that enough.

Cheat Code Cheat Description
Controls
mouseflip Inverts the mouse vertical rotation direction
shakey Toggle screen shake when units die
time toggle Turns the mission timer on or off (campaign mode only)
Difficulty Levels
hard Sets difficulty to hard (replaces previous difficulty)
normal Sets difficulty to normal (replaces previous difficulty)
easy Sets difficulty to easy (replaces previous difficulty)
let me win Causes you to win the current mission (campaign mode only)
Misc. & Info.
build info Tells you the date when the game was built
count me Prints the number of objects in the game
demo Starts demo mode - See "Additional Cheats" for description
droidinfo Shows unit info & stats
no faults Audio Clip - "There are no faults in the renderer at the moment"
sensors Shows sensor ranges when sensors are selected
timedemo Shows game info & stats
showorders Shows current order & action for selected droid (2.2 or later)
clone wars Creates multiple copies of selected unit(s)
Power
more power Adds an additional 1000 power
superpower Maximum power
whale fin Toggles infinite power
Research
give all Allows you to build & research everything
research all Gives you everything researched (2.1 or later)
work harder Finishes all active research
Strength & Damage
biffer baker Your units are stronger & deal more damage (replaces previous difficulty)
double up Your units are twice as strong (replaces previous difficulty)
get off my land Kills all visible enemy units & structures on the map
kill Kills the selected units/structures
reload me Immediately reloads currently selected unit/structure
Weather
deity Lets you see everything on the map (equivalent of having Uplink Center)
john kettley Changes the weather to rain, snow, or clear. Keep entering code to cycle weather.

A number of new keys are also available in the debug/cheat mode. These can cause game-play instability!

• k Flips the tile height.
  
• w or a Raises or lowers the tile height.
  
• y Demo Mode. Selects the team closest to the camera to start out with. The camera view will then randomly change from unit to unit & team to team. Your team will have an AI applied to it when selected. Same as the demo cheat.
  
• ctrl+o Opens up an options dialog that allows you to place units, structures, & features in game. Also allows you to switch to & take control of an enemy AI team.
  
• ctrl+y Shows the game info & stats. Same as the timedemo cheat.
  
• ctrl+x Completes all currently active research. Same as the work harder cheat.