My thanks to Tom McIntyre for this one.

In the beginning was the .357 Magnum, and it was good, and then the .44 Magnum, which was much better, and made Clint Eastwood famous and Elmer Keith happy. Eventually, though, rumblings of discontent were heard throughout the land, and there followed the .454 Casull, and the .475 Linebaugh, and the .480 Ruger, and the .460 and .500 S&W, and hand surgeons everywhere rejoiced. But in Switzerland, a gentleman named Zeliska felt the need for something bigger, and so he went, money in hand (lots of money) to the firm of K. Pfeifer Waffen in Feldkirch, Austria and Herr Pfeifer did him proud.
The Pfeifer single-action revolver is chambered for the .600 Nitro Express cartridge. This round, which dates from the early 20th century, is an elephant whomper so extreme that very few rifles have been made for it. The .600 fires a 900-grain bullet at 1,950 fps, produces 3 1/2 tons of muzzle energy, and is three times more powerful than a .500 S&W magnum.

The Pfeifer revolver weighs 13.3 pounds, is just under 22 inches long, has a ported 13-inch barrel, walnut grips, and gold-plated hammer, ejector, screws, and cylinder pin. The rear sight is adjustable, and the price is $16, 501. If you’re not man enough to hack the .600, you can get the gun in .458 Winchester, but you should be wary of also developing an interest in Judy Garland recordings and Broadway musicals.
Personally, I will wait until Herr Pfeifer comes out with a .50 BMG version. Watch the video to see the .600 in action.