At the top of my list of the odd firearms in the American firearm industry, is the Dardick Model 1500 revolver.
Cloud Gun – A multiple barrel gun firing projectiles at an extremely high rate of fire in the form of a dense cloud. Filed in August 6, 1987 and Issued June 6, 1989.
Multiple Tier Ammunition Magazine – detachable ammunition magazine for high rate-of-fire that stores and feeds triangularly shaped cartridges. Filed July 8, 1987 and Issued May 23, 1989.
Energy Transfer Multi-Barrel Gun – multiple barrel, rapid rate of fire, employing triangularly shaped cartridges. Filed July 30, 1987. Issued June 7, 1988.
Other inventions he patented that is not related to firearms:
The following is an excellent review of the historical and hard-to-find Dardick 1500 revolver: