M247 GP Machine Gun
From Halopedia, the Halo wiki
Summary
The M247 is a heavy machine gun that is normally seen as a stationary gun emplacement usually placed near defensive positions surrounding bases and fortifications. Capable of spewing out an incredible number of .30 cal rounds, the M247 turret makes quick work of anything foolish enough to get in its path.
There are several iterations of the M247. A brace-mounted M247 is easily portable and can be folded up and moved from location to location by a single marine. Another is attached to a swivel-turret, user guard, and ammo drum. The M247 also comes with a number of attachments, such as a 25mm grenade launcher.