Master gunnery sergeant
From Halopedia, the Halo wiki
Template:RealworldTemplate:Rank InfoboxMaster Gunnery Sergeants are sometimes referred to by the nickname "Master Guns" or "Master Gunny." These nicknames are unacceptable in formal or ceremonial situations, and, at the rank holder's discretion, may also be unacceptable for use by lower-ranking Marines.
