Replica Thompson Submachine Gun
Archaic weaponry of this type has seen a curious resurgence via the popularity of a number of holonovels that depict ancient periods of Earth's violent history. This particular weapon has something of a cult following among avid fans of the "Dixon Hill" holonovel series which rose to prominence after the publishing of an unauthorized biography of the Starfleet career of a former captain of the U.S.S. Enterprise-D, Jean-Luc Picard.
Though only a replica, this item has (perhaps unwisely) been fully modified to act as a corollary to modern weaponry, and may be used effectively in modern combat scenarios. It features multiple fully automatic firing modes.