Three words: MASSIVE HAND CANNON!!
A guy at my range has one. Brings it out every so often and lets people fire a round through it (the Hornady .460 rounds are crazy expensive). It will also function as a more normal revolver with .45 Long Colt or .454 Casul.
When you fire it (with the Hornady .460 rounds), it gives off a kind of 360 degree shockwave of BOOM! Huge muzzleflash as well. I've posted something like this before, but this might give you some idea:
Regular .45 ACP ammo:
GLOCK 19 9mm with some `flashy` ammo:
Short barrel 12 guage:
Shorty AR-15 with muzzlebreak (a known "big boom" combination):
.460 S&W:
Before:
After:
Some other shots of the .460:
You can also check out the videos that some of these photos are from on Youtube. The videos cannot even begin to convey the sound, the pressure wave and the flash involved in shooting these, however.
http://www.youtube.com/watch?v=AVmLiKsfZLo
http://www.youtube.com/watch?v=CWkzIvntxrc
http://www.youtube.com/watch?v=bzo8LlQdWJU