It's hard to believe it took this long for something like this to evolve.  Bullpup designs have been around for a hundred years, though admittedly rare in 1900. Tactical accessory rails are now dated.  Plastic guns have been around forever.  But all that in a pump shotgun, that and more in the Kel Tec KSG.

Kel Tec KSG

The magazine is revolutionary, too.  2 tubes under the barrel hold 7 shots each, selectable with a switch on the receiver.  That makes this gun light (it's made out of plastic), short (the bullpup configuration puts the receiver at your shoulder, giving you an 18 inch legal barrel, while still being as short as any sawn off shotgun), and carrying more ammo than two shotguns.  I wasn't a fan of Kel Tec it their early days, and I thought their little carry guns unreliable.  Time has proven me wrong, and they make guns as good as anyone.  This shot gun seems to be a pretty interesting design, but a bit expensive.  On Gunbroker, they rarely go under 1200 bucks.  Slick design nonetheless.

My buddy Ric sent me the link to this video from 2BrothersAdventures