Royal Marine (British Special Forces). Known to each other as "Royal" but the rest of the British Forces know them as bootnecks. This nickname is derived from them cutting the top from a leather boot and wearing it like a modern neckbrace to stop sailors cutting their throat while they guarded officers on board British sailing ships in the days of old.
"Don't anoy those Bootnecks over there unless you want to wake up with a crowd round you!"
A Royal Marines Commando.
The name comes from the old style Royal Marines uniform, which had a leather neck collar.
USMC can't get the job done? Send in the Bootnecks.