M68 Gauss cannon

The M68 ALIM is a weapon that fires hypervelocity, high-density projectiles similar to those of a MAC gun, except at a much smaller scale. It is mounted on the rear of the M12G1 Warthog LAAV. It is very powerful and very useful against vehicles. However, it is not as effective against infantry as the M41 LAAG, which is also mounted on the Warthog. This is because there is little splash damage and it has as slower rate of fire, but a direct hit will kill most enemies in one shot, two if they have an overshield. Due to its power and speed it is a good weapon against Wraiths and many other vehicles. It is similar to the 102mm SC-HE Rocket Turret of Halo PC.

This weapon uses a set of electromagnets to propel a 25mm slug of depleted uranium, a very dense, heavy metal, at high speeds. The raw mass and great speeds of the projectile is the key to the stopping power and performance of the Gauss cannon. Unlike the chain-fed system that the M41 LAAG uses, this cannon uses a tube to draw slugs from it's ammunition drum mounted below the cannon. Also, the electromagnets are powered by a multi-charger that is mounted in the drum that spins. There are four of these, for rapid fire because they overheat in one shot. It takes about a half a second to spin the drum and switch chargers.

In Halo 2, this version of the Warthog seems to have replaced the M12A1 LAAV version of the Warthog, which featured three Rocket Launchers. That version became problematic due to the prodigious reload time necessary for the launchers.

The Gauss Warthog made its debut in Halo 2 and returns in Halo 3

Trivia

 * It is possible to knock a Covenant Sniper Tower off its anti-grav pod by shooting it with the Cannon. Using this map on the Halo 2 multiplayer map Relic once the tower is knocked down, if someone new joins the game on their screen/console the sniper tower will still be in its original place. If you move around the knocked down tower with something like a Spectre, the tower that is still in place will move with the knocked down one mirroring its motion. The tower that was in place on the persons who joined after the first tower was knocked down will appear to be rolling around by itself.
 * Using the Gauss Cannon you can make a Combat Barrier bounce around by shooting the base of them.
 * During the Halo 2 demo trailer, the Gauss was shooting at a fairly decent speed. Later, in an early beta multiplayer phase the Gauss seemed to be slowed down and also seemed to have lost all of its hype. It was later revamped to its original rate of fire during the game's final stages.