Stinger Manufacturing, located in Saulte Sainte Marie, Michigan, has made a niche for themselves as a manufacturer of very small handguns. They are the manufacturer of the Pengun, a single-shot .22 caliber pistol that looks like a pen until it is reconfigured for firing, and the Survivor, a single-shot .22 caliber in the shape of a pocketknife. Their latest product is the Liberator, which is billed as "the smallest pistol ever." Whether or not that is literally true, it is very small - 2.25" x 3.30" x 0.90", the same height and width as a credit card (although, obviously, much thicker).
I don't know that these gadgets will really see much in the way of practical application, but they are rather cool in an "I want sharks with friggin' laserbeams strapped to their friggin' heads" kind of way.