Arsenal had this knife gun on display at SHOT Show. The .22 LR revolver is hidden inside the knife grip. Actuating a lever that extends out of the grip fires a round. Because the trigger-lever is forward of the chamber/cylinder, this is technically a bullpup revolver. It is considered an AOW (All Other Weapon) because it is a gun concealed inside another object.
A cleverly placed needle-like spike insures you don’t accidentally place your finger over the barrel.
The price: a mere $4,000 + $200 NFA tax.
Many thanks to Todd for the photos.