Dieter Michael Krone—a paper airplane aficionado with a pretty retro website—created a gun that folds and shoots paper airplanes. I'm not sure when you would need to rapid-fire dozens of tiny folded planes, but it's still pretty cool! 

Krone made the invention using mostly 3D printed parts, as well as parts from the local hardware store. At the end of the video, he shows the underbelly of the machine, giving the viewer a peek at how it all works. Watching the conveyor belt in action is extremely satisying. 

[h/t: booooooom.com]