Pistol

The M6G Personal Defense Weapon System (abbreviated M6G PDWS), otherwise known as the M6G Magnum Sidearm, is a United Nations Space Command infantry firearm, and is is one of the variants of Misriah Armory's M6 sidearm series.

Pictures
http://images1.wikia.nocookie.net/halo/images/thumb/d/dd/BnetH3pistol.jpg/300px-BnetH3pistol.jpg