The Liberator is the world's first successfully printed, assembled, and fired gun.
The Liberator isn't so much an actual pistol, but more of a zip gun. Though The Liberator does fire bullets.
Source: defcad.org
The Liberator has the size and accuracy of an improvised weapon (pictured below), but it is deadly.
Source: busaccagallery.com
It fires a small .380 caliber bullet. You can download files to make one on a 3D printer if you have one.
Source: defcad.org