A big, nasty hybrid gun, a revolver that shoots shotgun shells, was found in a "gangster gun room" in Taiwan (not sure what "gangster gun room" means exactly, the Google translation is hard to decipher). Can't buy one of these in a gun shop, but the black market price goes for approximately $6200 – $9300 USD.
According to Neatorama,
"Revolvers that fire shotgun shells are not a new idea. In fact, Taurus sells one called "The Judge" that fires .410 bore shells. What makes this handmade revolver from Taiwan unique is that it fires the much larger 12-gauge round."