Gunnery Sergeant (UNSC)
From Halopedia, the Halo wiki
Gunnery sergeant is the seventh enlisted rank in the UNSC Marine Corps, just above Staff Sergeant and below Master Sergeant, and is a staff Non-commissioned officer. Their common duty is to help some of the higher ranked officers such as Captains.
Gunnery sergeants are commonly referred to by the informal abbreviation "gunny." This nickname is usually regarded as a title of esteem and/or cameraderie, and is generally acceptable for use in all situations except formal and ceremonial ones. Use of the term by lower-ranking personnel, however, remains at the gunnery sergeant's discretion.
