Browning Machine Gun. I think that's not a REAL gun. It would probably break every bone in your hand, and several elsewhere. Surgery may be required to remove the front sight from the shooters forehead.
Maadi-Griffin used to make a pistol chambered for the .50 BMG before they got rail-roaded by the Feds. Supposedly, the recoil really wasn't that bad.
When I picked up the 500 the dealer explained that I might want to change out the grips as the recoil was subject to cut the area between thumb and forefinger. However, my husband describes the Ruger 480's recoil to be considerably worse that the S&W 500's. I haven't shot either as I'm partial to long guns and not too fond of wrist pain.
Maadi-Griffin did make a .50 BMG handgun, but it had a massive muzzle brake at the end (and I forget whether it had a stock of any sort).