The Give command brings forth an item or object, player or enemy. To 'give' an object, push the Tilde key [~] and type "Givex" where x is the singular form of the desired item (without spaces).

Here are a few examples:

All
Ammo
Armor
Armor Shard
Blue Key
Body Armor
Combat Armor
Commander's Head
Health
Invulnerability
Power Cube
Power Shield
Red Key
Security Pass
Silencer
Slugs
Weapons