The brute shot

The Brute Shot is has a rather peculiar design, as the user carries it low, rather than using the hilt or handle of a weapon. It has a quite fast firing rate for a grenade launcher; capable of firing four grenades in around three seconds. It, like the other Brute weapons, has a blade slung onto the bottom of the weapon to increase the melee damage. The Brute Shot can hold up to 18 rounds, with 6 in the gun itself.
[edit]Ammunition
It seems to fire a type of grenade similar to the Frag Grenade at very high velocities that bounces off of and around most surfaces, although originally it was supposed to shoot plasma grenade like projectiles. It was first encountered during Battle of the Flood-controlled Shield World, where it was used to a deadly effect against the crew of the Spirit of Fire. The grenades seem to be belt fed through the top of the weapon. The splash damage from this weapon is extremely high, and it also has a very sharp curved bayonet near the back on the underside of it, which is used as a powerful melee weapon. This blade delivers a higher than normal amount of melee damage.I have got this info from halopedia.com