These tiny Austrian 2mm pinfire guns look to be exquisitely engineered. From the video description:
Originally made by Austrian watchmakers as decorative pocket watch chain fobs or as cufflinks, these miniature pinfire pistols are now prized collector's items. These are some from my own collection dating from 1904 to the 1970's. All of them fire 2mm blank pinfire cartridges. The revolvers are the world's smallest working double action blank firing pistols. They measure just 38mm in length and are smaller than the famous Swiss Mini Gun which measures 55mm.