The Tesla Gun is a hand-held, battery powered lightning machine. It is a spark gap Tesla coil powered by an 18V drill battery. You pull the trigger, and lightning comes out the front.
It is functionally inferior to that of Tesla’s design in the Five Fists in a few important respects. Notably, it is a bit longer and heavier than Tesla’s own. It also cannot (yet) create an ion wind strong enough to cushion the user when leaping from a four story building.