Gravgun

Grav-gun are weapons that directly affect the local gravity of the target. The heavier the targets weapons and armor the greater its affect.

It is range 18' S* AP2 Salvo 2/3 with Concussive and Graviton.

With the Graviton rule the gun doesn't roll to wound like normal, instead it wounds based on the targets armor save. For example anything with a 2+ will be easily wounded, while stuff with a 5+ will be harder to wound. When rolling to penetrate against vehicles a 1-5 will do nothing however a 6 will instantly immobilize it.

In the fluff the current Grav-guns, and Grav weapons in general are based off the designs of ancient grav-weapons employed by the space marine legions. Only a select few know the secrets of their constructions and maintenance and only the most trusted and promising techmarines are trusted with them.

While they can easily kill heavily armored units they are largely useless against light armor. For example a plasma can be reliably counted on to deal with virtually anything from terminators to guardsmen. It is ideally suited for one kind of target but can still be used effectively against others. Grav-guns on the other hands are good against one target and only that target. It will shred through 2+ 3+ or even 4+ saves but completely stall against anything with a save worse then that. For this reason the weapon is largely panned by marine players as too situational to be effective.