Type "money" at the inventory screen to get an instant $5,000. This can be used indefinitely.
Type "moon" when in third-person for a HUD map. Very helpful when avoiding infantry rockets.
Type "design" during the placement stage, before the mission has begun. Here you can edit platoons and such. Fairly straight forward, use the right mouse button to bring up options. This can give you INCREDIBLE numerical advantage over your enemy!