Sub machine guns. Though with the low impact high fire rate auto rifles that there are, I doubt it. Otherwise there isn't much more they could do. Grenade launcher, some kind of constant laser beam? Idk. They pretty much covered each major type of gun I can think of. The rest are pretty much just variations like say a mini gun. Which would basically be the same as the low impact machine gun. Normal pistols are about the only thing but they would need to be in unrealistically overpowered to compete with other primary weapons.