Just my opinion, but any of the pistol caliber carbines like a beretta cx storm. Seems useless unless you are a person that doesn't want to learn to adequately shoot a handgun. ARs in pistol calibers? That's another story. At least there you get AR modularity and extended mag size. I just don't understand carbines that are loaded just like a pistol (through the grip) with pistol sized magazines.
9mm performs like it ought to from a SMG length barrel IMO, so SBR's in pistol caliber are nice and give the user more control than a handgun.