Assault cannon

Looking for the closely related Covenant vehicle weapon, Fuel Rod Cannon or for the Fuel Rod Gun?

The Assault Cannon is a variant of the standard Fuel Rod Gun utilized only by the Mgalekgolo. It has two variants, one of which is all but identical to the normal Gun, the other of which is closer to the vehicle variant and fires a continuous beam.

Design Details
The weapon is incredibly heavy, making it suitable only for the Hunters, as no other races could carry such a massive load. The only known instances of it are fused directly to the Hunter's armor, located on the right "arm" of the colony, built into the Lekgolo that make up the limb. This makes the weapon impossible to be used from the player in any game.

Ammunition
The ammunition it uses is tubes of radioactive incendiary gel, very similar to those fired by the standard Fuel Rod Gun. The gel can be fired in globs, as seen in Halo: Combat Evolved and occasionaly on Halo 3: ODST, which detonate on impact and have an arcing trajectory. The weapon can also fire the gel in a 'beam', as seen in Halo 2 and 3. It is presumed that the weapon itself can switch between these two modes by the Mgalekgolo using it. However, before firing, the weapon must be charged up. This "charge" makes it very obvious that the Hunter is attempting to shoot an enemy, and it also makes it fairly easy to dodge the cannon's blast for players in the Halo trilogy.

In terms of gameplay, the Assault Cannon has changed in each version of Halo, in terms of operation and aesthetics, mostly to balance out the gameplay with other weapons. It is unknown how the Hunters make the beam fire, there may be a trigger inside the gun that they pull to fire the weapon or some type of neural link.

Variations Between the Halo Games
In Halo: Combat Evolved, it was only able to fire single shots that were similar to fuel rod shots, and appeared to contain its gel supply in a "drum" mounted underneath the arm.

In Halo 2, there were minor changes to its appearance but the weapon fired a continuous stream rather than individual blasts while the "drum" reloaded and fired.

In Halo 3, the Assault Cannon is aesthetically very different, but operates much the same as it does in Halo 2. The cannon in Halo 3 can be cut off instantaneously if the target has gone to cover, which stops it from wasting ammunition. Also, the "claws" seem to have hinges, although they are never seen moving in gameplay. Plus, the beam is a bit faster, a lot more damaging, and can blow away movable cover, such as supply crates. They are also still extremely easy to avoid.

In Halo 3: ODST, the Hunters appeared in two different forms in two different colors; the blue-armored Hunter, armed with an assault cannon that fires a continuous stream of radioactive incendiary gel and a gold-armored Hunter, armed with an assault cannon that fires a single bolt of radioactive incendiary gel which is similar to the weapon model featured in Halo: Combat Evolved.

In Halo Wars, the Hunters start with the mortar version of the Assault Cannon. Later in the game, the Hunters can be equipped with the Assault Beam for extra damage.

Trivia

 * The Halo Custom Edition mapping team featured a usable Assault Cannon in both versions of their modded campaign levels.
 * When using the Bump Possession cheat in Halo: Combat Evolved to control a Hunter, holding left click down and repeatedly right clicking allows the controlled Hunter to rapidly fire its Assault Cannon without overheating. Whether this accelerated manner of attack is actually utilized at all in AI controlled opponents' behavioral patterns is unknown.
 * In Halo: Combat Evolved, Hunters will not continue to track you once the cannon has started to charge, making the Hunters inaccurate with moving targets. Strangely, Hunters will never hit a stationary target, meaning that the original Assault Cannon's recoil severely lowers the accuracy of the said cannon. You can use this to your advantage to avoid being injured by standing completely still and firing from that position.
 * In Halo 3, if you look closely at a Hunter's Assault Cannon when it is charging up, green electricity protrudes from the three parts jutting out of the weapon and they form together to make the beam of energy. It is also possible this would create a type of small plasma mortar, and that something in the back of the weapon produces a type of gas to project it, similar to how a Flamethrower works where a small flame is projected by gas.
 * The Halo 3 variant doesn't contain the "drum" like the previous Assault Cannons. Instead it has six tubes on the side of the gun which appear to house the incendiary liquid projectile.
 * Some of the novels refer to the Assault Cannon as a Fuel Rod Gun/Cannon, while it is officially named in Halo: Contact Harvest.
 * The High Prophets use a modified, yellow version of the Assault Cannon, which is mounted on their Gravity Thrones.