The M203 grenade launcher was a single shot grenade launcher that was designed for attaching to automatic rifles like the M16. It was made by Colt Firearms for the United States military. The M203 grenade launcher and its variants saw extensive service with the US Armed Forces from the 1960s to at least the late 20th century.
US Marine sentries used the M203 grenade launcher on board the aircraft carrier USS Enterprise. One of the marines had the launcher attached to his M16 as he was chasing Pavel Chekov. (Star Trek IV: The Voyage Home)