How about a .40 S&W caliber carbine?

[Bearcat]

After shooting my M&P today, I'd like S&W to build a nice, 16-inch barrel carbine in .40 S&W that would accept S&W high capacity magazines.....I'd buy one!

 

[missiondude]

Rock River Arms makes a 40 carbine, but it takes a proprietary magazine...

 

[Mule88]

a 10MM would be cool too.

 

[paco04]

Maybe something along the lines of a Marlin camp 9 or camp 45. The camp 9's already are capable of using 59 series magazines.