Master chief petty officer

Master Chief Petty Officer is the ninth enlisted rank of the UNSC Navy and is a non-commissioned officer. It is equal in rank to Master Gunnery Sergeant and Sergeant Major in the UNSC Marine Corps.

In informal settings, Master Chief Petty Officers are typically called "Master Chief."

Gallery
http://i523.photobucket.com/albums/w356/Marolessa/Halo.jpg A picture of the master Cheif with a Shotgun.(This picture is from Halo 2).