The .600 Nitro Express is the one of the largest of the Nitro Express rounds ever developed, second only to the .700 Holland & Holland Nitro Express. Originally meant for big-game hunting, its a round so powerful, it dents common handgun steel targets. As such, someone decided to build a handgun for it.
The .600 Nitro Express Zeliska Revolver is a single-action revolver from Pfiefer Firearms in Austria. The handgun can fire a 900 grain slug at 1,950 ft/s, making over 7,500 ft/lbs of muzzle energy. According to Wikipedia, the handgun costs about $17,000 and each .600 Nitro Express round costs $40, making this far and above more expensive than even the .50 BMG.
When someone has to wear a helmet to fire the revolver, I think the loading is just a wee bit too hot. But, equipped with gloves, helmet and a huge muzzle brake, a dare-devil goes against all better judgement and pulls the trigger. The results (and proof of his courage) is posted on YouTube for all to see.