T3-M4 utilizing a droid shock arm
A small attachment for a droid, known by several names including electro probe, droid shock arm, electro-shock prod, or electroshock probe, was capable of delivering a short burst of electricity. This discharge was strong enough to disable a computer terminal or a security lock. If this probe made contact with living creatures, it would cause them to become unconscious.
The R2-series astromech droid models manufactured by Industrial Automaton often included this probe as a standard component.
During the era of the Jedi Civil War, a T3-series utility droid called T3-M4 possessed a shock arm. Furthermore, numerous astromech droids were built with shock arms thousands of years later. Two examples of astromechs known to have this feature were R2-D2 and R4-P17.
Within the video game Star Wars: Knights of the Old Republic II: The Sith Lords, T3-M4 is the only character that can equip this particular item.