Arm-mounted Drill

The arm-mounted drill is an unconventional piece of weaponry used by shinobi from Yumegakure's Tenrō clan.
The weapon itself is a large drill which the user wears on their underarm, usually in a dual fashion. The drill can be used as a conventional thrusting weapon, adding extra damage as it spins, but also allows for swift underground movement, enabling the user to ambush opponents from beneath, similar to a number of ninjutsu.