That imposing figure above is Rob Flickenger, who's built his own battery-powered Tesla Gun based on the one wielded by Nikola Tesla in a graphic novel by Matt Fraction and Steven Sanders.
Flickenger says that he was inspired to build a real-world version of the Tesla Gun after reading a Steampunk graphic novel called The Five Fists of Science, that concerns the efforts of Nikola Tesla, Mark Twain and Bertha von Suttner to bring about an end to all war and the titanic battle for supremacy against the Dark Lords of Power – Thomas Edison, John Pierpont Morgan, Andrew Carnegie, and Guglielmo Marconi – that follows. [Gizmag]
Flickenger's Tesla Gun is longer, heavier, and not as powerful as the one in the book. It also can't create a cushioning ion wind for all your base-jumping needs. On the other hand, it exists in reality and can handle 20,000 volts and 2,000 amps while kicking out two-foot long freaking lightning bolts.
It's essentially a spark gap Tesla coil built upon an 18V drill and an aluminum case based on a Nerf gun. It has a 30 minute battery life and is not quite as dangerous as it sounds. Flickenger says a baseball bat is a more effective weapon, adding, "You’re a lot more likely to hurt yourself if you’re foolish enough to fire the thing. This is sculpture. Art inspired by art. Not a weapon, any more than any object is a weapon if wielded with intent to harm."
A video of the Tesla Gun firing is below along with more pictures of the build. For a more detailed run-down on exactly what went into this (besides massive cajones) check out the detailed explanations at Gizmag and Rob Flickenger's site. Chortling like a maniac is optional.
More pictures available at Flickenger's Flickr page.