I would have to chosen the gatling gun that Jesse Venture used in Predator. He carried all of it on his back thru the jungle, HAHAHA!
Last time I saw one in the Marines, it was hooked up to the helos power system just to run it and the gunner was sitting on an ammo box bigger than he was.
Of course, it was a movie and he did clear about an acre of jungle in one minute, something to think about when they attack in a giant human, I mean zombie wave.