Railguns are an actual real thing, but for most people, they're just a killer gun they used a lot in Quake. Which might explain why this guy went out and built himself a working, handheld version of the experimental weapon.
NSA_Listbot's 3D-printed gun (above) can blast out pieces of copper-plated tungsten (below) at around 220 miles per hour.
Here's what it looks like firing. Note the description: "I have no idea what happened to that piece of carbon- probably just vaporized."
Disregard how flimsy and unfinished that top image is, too. Here's the finished product, painted and with accessories included. Badass.
You can see more pics, gifs and videos of the weapon in action in this gallery.