Fludblud sends a link to his review of the Show Guns Tactical Shotgun Shell Launcher which is available right now at some airsoft retailers... "Here is my comprehensive review of a rail mounted airsoft shotgun shell launcher by Show Guns Tactical, complete with live subject testing. The device is extremely simple to use, lightweight and perfectly sized to fit on the underbarrel rail mounts of various airsoft sidearms. Intended to be used as an absolute last resort, the SG Tactical 20mm Launcher comes with one metallic PPS shotgun shell which carries six rounds, however it is also compatible with APS C02 shells as well.
Aside from a bit of fiddling with the safety, I ultimately consider it to be a fun novelty item to bring to CQB games though its the single shot nature means you have to save it up for the right moment."