master gunnery sergeant

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A noncommissioned rank in the US Marine Corps that is above master sergeant and equivalent to the position of sergeant major.
• noun One who holds this rank.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun military, US A non-commissioned officer of rank E-9 in the United States Marine Corps, ranking above a master sergeant/first sergeant and below a warrant officer. It is equal in grade to sergeant major