Barracks. Used to make infantry. Relatively weak.
Weapons factory. Used to make vehicles. Rather low on armor so protect it well.
Guard tower. If an enemy unit comes with in range of this powerful high velocity machine gun, they'll think twice before attacking again!
Advanced guard tower. Similar to the guard tower, this has a long range and fires missiles. Can also shoot air targets. If your power output drops below green, it won't fire.
Advanced communications center. This requires a lot of power, because it charges the orbital Ion Cannon.
Grenadier. Very useful for attacking over defences and other infantry, and somewhat good for vehicles.
Orca. Standard chopper for GDI. Equipped with 6 rockets, in a swarm of about 12, these babies are lethal.
Mammoth tank. Very good for raids in groups of 6 or more. These are heavily armored and come with dual cannon and missile racks. Needs close quarter protection.
Medium tank. Smaller, faster, and more versatile than the mammoth, this fires armor piercing shells. It is quite well armored.
Hum-vee. GDI's fastest vehicle, this has a weak minigun. Best used for scouting around in.
APC (Armored Personnel Carrier) Self explanatory, really. Quite fast, carries up to 5 troops to and from battle locations.
Rocket launcher. Very slow vehicle. Almost like a portable adv. guard tower, but weaker. Fires 227mm missiles (VERY powerful!). Needs close quarter protection.