A video by the website Papierfliegerei.de shows a man firing a 3D-printed machine gun that folds and launches paper airplanes.
A little tinkering from me that shows what you can do with 3D printers today. Most parts of this paper airplane machine gun had printed by fabberhouse.de (the rest of them are to buy via Internet or hardware store). By the way, I use a cordless screwdriver from China for driving.