I've got your patented zombie medicine right here, the KelTec KSG bullpup pump shotgun. Its kewl!
Need a pistol to keep you alive until you can get to your shotgun? U.S. Firearms M4-.410. Its so steampunk I can hardly believe it.
And what are we going to load our zombie slaying shotguns with? Zombie Blasters, obviously! ka-BOOM!