Halo Wars/USNC Units

Warthog
The Warthog is a fast ground vehicle that is given to you at the start of the game. It's good for scouting because of its speed. While it starts with the ram ability, it needs upgrades to allow it to attack from a range. It's best used to scout and collect resources or against light infantry.
 * Cost: 150
 * Damage: Medium
 * Supply: 1
 * Speed: Fast
 * Armour: Light/Medium
 * Shields: None

Upgrades

 * 1) Gunner - Cost - 250 - Tech Level - 1 - Adds a Machine Gun attack to the Warthog. Adds attack capabilities.
 * 2) Grenadier - Cost - 500 - Tech Level - 2 - Adds a Marine with grenade launcher. Improves attack.
 * 3) Gauss Cannon - Cost 800 - Tech Level - 3 -Replaces machine gun with a laser cannon for greatly improved attack.

Marine/ODST
The Marine is a cost-effective unit that can be massed quite easily. It's a cheap unit that can be stationed on towers and work great against air units. When the ODST upgrade is researched it turns marine squads to ODST squads. They are also able to be hot-dropped into battle and are way stronger and tougher than the marines.
 * Cost: 100
 * Damage: Low (Medium with ODST upgrade)
 * Supply: 1
 * Speed: Medium
 * Armour: Very Light (Medium with ODST upgrade)
 * Shields: None
 * Captain Cutter only

Upgrades

 * 1) New Blood - Cost - 200 - Tech Level - 1
 * 2) * Adds 1 more marine to the squad, improving effectiveness.
 * 3) RPG - Cost - 400 - Tech Level - 2
 * 4) * Replaces Special Attack Y grenades with Rocket Propelled Grenades that improve attack and can target air units.
 * 5) Medic - Cost 700 - Tech Level - 3
 * 6) * Adds a Medic unit to the squad, improving effectiveness and allows healing after battles. Cannot heal during battle and cannot revive fallen marines.
 * 7) ODST - Cost - 1,800 - Tech Level - 3 - (Captain Cutter Only)
 * 8) * These Orbital Drop Shock Troopers are improved from normal Marines in every possible way. They use Shotguns to attack and can be hot-dropped at will. ODST's are only available to Captain Cutter

Flamethrower
The flamethrower is an anti-infantry unit. It will do great against packs of marines and other infantry units. However, it can not attack air and its attacks are considerably less useful against vehicles. Mass this if your enemy is massing infantry.
 * Cost: 100
 * Damage: Low
 * Supply: 1
 * Speed: Medium
 * Armour: Very Light
 * Shields: None

Upgrades

 * 1) Flash Bang - Cost - 200 - Tech Level - 1
 * 2) * Flamethrowers gain stun grenades that stop infantry in their tracks, open for attack. Doesn't affect Convent Leaders, however.
 * 3) Napalm Adherent - Cost - 400 - Tech Level - 2
 * 4) * Improves attack and adds after burn damage.
 * 5) Oxide Tank - Cost 700 - Tech Level - 3
 * 6) * Greatly improves damage against infantry.

Spartan
The Spartan is a strong unit that can handle small groups of units easily. They can be outfitted with chain guns that make their damage increase quite significantly, and can also be upgraded with Spartan Lasers. Their initial starting ability is the vehicle hijack, which steals an enemy vehicle and gives it to you. You can only have three of these guys at any given time, but they don't use regular supply.
 * Cost: 300
 * Damage: Medium (High with Spartan Laser)
 * Supply: 0 (max of 3)
 * Speed: Medium
 * Amour: Medium/Heavy
 * Shields: Light/Medium

Upgrades

 * 1) Chain Gun - Cost - 300 - Tech Level - 2
 * 2) * Replaces the Spartan's SMG with mini-gun, improving damage.
 * 3) Neural Implant - Cost - 600 - Tech Level - 3
 * 4) * Allows for fast hijacking of enemy vehicles.
 * 5) Spartan Laser - Cost 1,000 - Tech Level - 4
 * 6) * Replaces Chain gun with a Spartan Laser, greatly improving damage.

Scorpion/Grizzly
Scorpions are the main vehicle unit, adept against infantry and against buildings as well. Their special ability launches a powerful attack against any ground target. They are slow however.
 * Cost: 500
 * Damage: High (Very High with Grizzly upgrade)
 * Supply: 3
 * Speed: Slow/Medium
 * Armour: Heavy (Very High with Grizzly upgrade)
 * Shields: None

Upgrades

 * 1) Canister Shell - Cost - 400 - Tech Level - 3
 * 2) * Adds a special Y ability to the tank, allowing a secondary cannon attack, devastating to buildings and other vehicles.
 * 3) Power Turret - Cost - 900 - Tech Level - 4
 * 4) * Improves the main turret's turning speed.
 * 5) Grizzly - Cost - 1,800 - Tech Level - 4 (Sergeant Forge Only)
 * 6) * This "Grizzly" of a tank improves the tanks attack power versus infantry, spreads out it's Canister Shell ability, and improves it's health points.

Cobra
The Cobra is the UNSC's anti-vehicle unit. It does mild damage normally, but when locked down, it's damage improves massively. In addition to dealing great damage against vehicles, it can tear buildings apart.
 * Cost: 350
 * Damage: Low (High when locked down)
 * Supply: 2
 * Speed : Slow
 * Armour: Medium (High when locked down)
 * Shields: None

Upgrades

 * 1) Deflection Plating - Cost - 400 - Tech Level - 3
 * 2) * Adds extra protection while locked down and may reflect projectiles.
 * 3) Piercing Shot - Cost - 900 - Tech Level - 4
 * 4) * Improves rail gun damage to damage multiple targets.

Wolverine
The Wolverine is the UNSC's anti-air unit. It does good damage against anything that flies but low damage to other units. It's volley attack can help damage against vehicles and buildings.
 * Cost: 300
 * Damage: Medium
 * Supply: 2
 * Speed: Medium
 * Armour: Light-Medium
 * Shields: None

Upgrades

 * 1) Volley - Cost - 400 - Tech Level - 3
 * 2) * Adds a Special attack to the Wolverine. Allows a large missile barrage attack on ground units and builds, but cannot attack air units.
 * 3) Dual Launchers - Cost 900 - Tech Level - 4
 * 4) * Adds another set of missile pads to the Wolverine, greatly improving the damage.

Hornet/Hawk
The UNSC's main flight unit is fast and agile, but is very easy to be taken down. However, it can be upgraded with two marines on the side plates and chaff pods, which reduce the chance of missiles hitting it. These aircraft are good against enemy vehicles and lone infantry. Either use these in groups or have them go with ground units, otherwise enemy fire will concentrate on the hornets and you will lose them.
 * Cost: 250
 * Damage: Medium
 * Supply: 2
 * Speed: Fast (Flight)
 * Armour: Light
 * Shields: None

Upgrades

 * 1) Wingman - Cost - 400 - Tech Level - 3
 * 2) * Wingman adds two marines carrying rocket launchers to the Hornet, improves attack power.
 * 3) Chaff Pod - Cost - 900 - Tech Level - 4
 * 4) * Chaff Pod adds the passive ability to dodge rockets and missiles.
 * 5) Hawk - Cost - 1,350 - Tech Level - 4 (Professor Anders Only)
 * 6) * Upgrade to the hornet equipped with a mounted laser for greater damage.

Vulture
This is the UNSC's Uber unit, which can be upgraded with 2× missile silos, which doubles the damage for the secondary attack. Its primary attack uses two dual-cannons at the front of the ship, and the secondary attack fires lots of missiles at your target. Just one of these can take down a base!
 * Cost: 900
 * Damage: High
 * Supply: 6
 * Speed: Medium (Flight)
 * Armour: Meduim
 * Shields: None

Elephant

 * Cost: 400
 * Damage: Medium
 * Supply: 2
 * Speed: Very Slow
 * Armour: Heavy
 * Shields: None

This is a mobile base that can be deployed using the secondary attack button. Once deployed it can create all infantry units. It can be upgraded with better engines, better armour and a machine gun turret that only works when deployed.