Unggoy Heavy

Gunner Grunts or also referred to as Heavy Grunts by some are a Covenant Unggoy rank equivalent to an UNSC technical Sergeant. This rank is designated for use of heavy weapons and turrets.

Armor
Heavy Grunts wear distinctive emerald, greenish armor with a methane breather, but are otherwise similar to other Grunts in terms of armor style. They take much more damage than Grunt Minors and Grunt Majors, but not as much as higher ranking Grunt Ultras and SpecOps Grunts.

Combat
Heavy Grunts are usually seen in conjunction with other Covenant infantry, operating as heavy support units, and usually operate heavy weapon systems such as Plasma Cannons, Shades, and Fuel Rod Guns with deadly effect. They usually will not flee from their position unless 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 easily dispatched using most tactics, though their armor seems to be tougher than the average Grunt, most likely to protect them from explosives and other heavy weapons fire. Unlike most Grunts, they will rarely throw Plasma Grenades.

Note that the cannon is free for you to use after taking out its operator. In Halo 2 a Heavy Grunt must first deploy its Plasma Cannon before it can be used. If the Grunt Heavy carrying the Plasma Cannon is killed before it can deploy it then it cannot be used. This is not the case in Halo 3 since most of the Plasma Cannons encountered are already deployed with the exception of few, and can still be used even if they are detached from their tripod.

In Halo 3 Grunt Heavies are seen utilizing many different heavy weapons and vehicles. They are commonly seen driving Ghosts, and seem to be very skilled drivers, especially on higher difficulties. Grunt piloted Ghosts can be a fearsome and deadly presence on the battlefield. Grunts will attempt to ram enemies and will keep their distance from advancing foes. Usually if they're not piloting a Ghost then they're manning a turret or carrying a Fuel Rod Gun. They can be hard to kill with small arms when they are piloting a Ghost because of their great maneuverability and speed.

Like SpecOps and Ultra grunts they are some of the most dangerous Unggoy. When not manning a vehicle or turret or carrying a Fuel Rod Gun, Grunt Heavies will usually use Plasma Pistols. They are very efficient with these weapons, even overcharging them which is uncommon among Unggoy. They will even try to aim for Headshots, even though none of the weapons they are encountered using, are capable of even getting one.

Grunt Heavies are fearsome enemies, especially on the Heroic and Legendary difficulty settings where their heavy weapons can make short work of the player. Their lethal efficiency with anything they use has coined the term "Green Grunts are Horrible People"; a widely used term on Xbox Live.

Appearances
Heavy Grunts have been seen only in several levels of Halo 2 and Halo 3:

Halo 2

 * Cairo Station - Two Heavy Grunts at Hangar A-02 and three at Commons B-01 man Plasma Cannons.
 * Outskirts - Three Heavy Grunts are found manning plasma cannons in the tunnel.
 * Delta Halo - Four Heavy Grunts man Shielded Plasma Cannons at the beginning of the level, defending against 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 deadly Fuel Rod Guns, except for the two Gunners at the start of the level. You can find them also when your at the second grav-lift that takes you across, not up, supporting three Spec Ops Elites.

Halo 3

 * The Storm - Seen on the Scarab on higher difficulties manning plasma turrets and on the last part of The Storm carrying a plasma turret which it will set up when his comrades see you when you go to take out the Covenant AA gun. They are also seen piloting the Ghosts dropped off by the Phantom to give support to the AA Wraith
 * The Ark - Seen in many points throughout the level, they drive many of the light vehicles and operate plasma cannons from many positions, including two atop a Gravity Platform in the beginning area. There are also two with Fuel Rod Guns half way into the level
 * The Covenant - Depending on the difficulty, two Heavy Grunts armed with Fuel Rod Guns defend each of the hallways that lead to the Prophet of Truth. The first area in the hallway, on Legendary, three heavies, two with a fuel rod, the other with a turret will arrive as reinforcements. In the next hall, two of them are fighting with the Brutes. They both wield Fuel Rod Guns. The Heavy Grunts on this level pose more of a problem than other ones as they hang back and decimate your forces with Fuel Rod Guns, Battle Rifles are an effective way to take them out.
 * Most Shades in Halo 3 are operated by Heavy Grunts, appearing in most levels. Ones not operated by Heavy Grunts are operated by Grunt Minors.
 * In every level (excluding The Covenant) Heavy Grunts are seen operating the plasma cannons on enemy Phantoms. A couple of Battle Rifle bursts is a good idea here to limit the incoming fire from the Phantom.
 * Also, there were Shades in Halo Combat Evolved and therefore Heavy Grunts, but the grunts themselves were never seen.

Trivia

 * They are rarely seen wielding the Spikers. This is easier to find when the player destroy a Phantom, the Grunt will most likely (if it had survived) be wielding a Spiker.
 * The only time a non-Heavy Grunt is seen deploying a Plasma Cannon is in Halo 2 at the beginning of the level The Arbiter, where a Spec Ops Grunt is seen carrying one. This is because the only Unggoy allies encountered in the level are Special Operations Grunts and one Ultra Grunt.
 * In Halo 2, Heavy Grunts carry Fuel Rod Guns with two hands and they still do in Halo 3, but when the player sends a Heavy Unggoy with an un-deployed plasma cannon, in panic mode, they run around with the cannon in one hand. This could mean that the fail safe on them (which presumably have been removed in Halo 3 as the Master Chief and his allies can use them) is switched off.
 * No Heavy Grunts appear in Halo: Combat Evolved.