Nothing says "home defense of the future" quite like a fully-automatic weapon that uses electromagnetic coils to fire ferrous metal slugs.
In Mechwarrior lore, the Gauss rifle is one of the most feared weapons on the battlefield. It fires metal slugs at extremely high velocities for unparalleled range and accuracy, and because it doesn't rely on ammunition propellant or explosives, it's relatively safe and easy to keep fed. The downside is that it takes a whole lot of power to move those slugs at a useful speed, making them big, heavy weapons - not the sort of thing you carry around in your back pocket.
Jason Murray's Gauss gun doesn't pack enough of a punch to bring down a giant fighting robot (and possibly not even a guy in a heavy winter coat) and the accuracy doesn't appear all that hot either, but the simple fact that it works as well as it does is mightily impressive. Powered by a pair of 22.2 volt Lithium-polymer battery packs, his "CG-42" fires caseless steel slugs at a rate of 7.7 rounds per second with a muzzle velocity of just under 140 feet per second - a small fraction of the 1400-ish ft/s velocity of a conventional handgun round but still enough to mess up your day, especially if it hits home in a sensitive area.
But more important than any of that, it's stupidly cool - this is an actual Gauss machine gun, designed and built by a single guy who has a thing for "making concepts from science fiction become reality." It looks great, too. I'm not really what you'd call a "gun guy" but this is definitely something I'd love to have hanging on my wall.
Source: Delta-V Engineering