M68 Gauss cannon

The M68 Gauss Cannon is a weapon that fires hypervelocity, high-density projectiles similar to those of a MAC gun, except on 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 reasonable rate of fire it is a good weapon against Wraiths and many other vehicles. It is similar to the 102mm SC-HE Rocket Turret of Halo PC but shoots like a miniaturized version of the MAC cannon

This weapon uses a set of electromagnets to propel a 25mm slug high speeds. The great velocity of the projectile is the key to the stopping power and performance of the Gauss cannon, giving it unparalleled armor penetration.

In Halo 2, this version of the Warthog seems to have replaced the M12A1 LAAV version of the Warthog, which featured a triple barrelled rocket launcher. 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
the halo 3 version of the guass cannon is stronger but slower
 * It is possible to knock a Covenant Sniper Tower off its anti-grav pod by shooting it with the Gauss Cannon shot.
 * 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
 * In Halo 3, the slug in mid flight is blue with a blue tail making it look Covenant weapons fire at first glance. This 'blue light' is mostly like the slug heating the air around it to super heated levels from the friction and heat of the slug.