Unggoy Heavy

Grunt Heavy is a Covenant Unggoy (Grunt) rank.

Armor
Heavy Grunts wear distinctive green armor with methane breathers, but are otherwise similar to other Grunts in terms of armor style.

Combat
Heavy Grunts are usually seen in conjunction with other Covenant infantry, and most often operate a Plasma Cannon, hence their name. However, sometimes, they will wield a Fuel Rod Cannon.

They usually will not flee from their position until the player is too close or out of range of their weapon, in which case they will pull out a Plasma Pistol and attack like a normal Grunt. They are easy to kill with any method you use, though their armor seems to be tougher than the average Grunt. Most likely to protect them from explosives from their Fuel Rod Cannon. Unlike most Grunts they will not usually throw Plasma Grenades ,they will but rarely.

Note that the cannon is free for you to use after taking out its operator. However, the Heavy Grunt must deploy a cannon on a tripod before operating it, and if killed before deploying a cannon, the cannon is inoperable.

In Halo 2 they are green but in Halo 3, it would seem as though they are a more turquoise color.

In Halo 3 these grunts can be a big threat. They are commonly seen driving ghosts, and they are very skilled at it, much better than any marine. Just one ghost can easily kill the player. If you try to board it, the grunt driving it will back up and fire it continuously just like a player would in multiplayer. Usually if they're not in a piloting a ghost then they're manning a turret or carrying a a Fuel Rod Cannon.

Appearances
Heavy Grunts have been seen in Halo 2 and Halo 3:
 * Cairo Station - Two Heavy Grunts man Plasma Cannons at Hangar A-02
 * Delta Halo - A handful of Heavy Grunts man Shielded Plasma Cannons at the beginning of the level, defending against an attack by SPARTAN-117 and Orbital Drop Shock Troopers.
 * Gravemind - Several Heavy Grunts are deployed to take out the Master Chief, all are equipped with the deadly Fuel Rod Cannons, except for the two Gunners at the start of the level. During the opening cutscene for the level, a heavy grunt is seen videotaping the High Prophet of Truth during his speech, and later runs away in terror once the Master Chief arrives.
 * The Covenant - Depending on the difficulty, two Heavy Grunts armed with Fuel Rod Cannons defend each of the hallways that lead to the Prophet of Truth.