No no no, you gotta think long term. Where are you gonna find ammo for a gattling gun while hiding out from zombies. LOL, a turret mounted street sweeper would be cool, shotgun shells are everywhere!!!
So if we can convert the gattling gun to an auto shotgun, we are good to go. Thought about a flame thrower, but a zombie on fire sounds like a bad idea.
I found a water purifier built by Dean Kamen, the Segway guy,that can get safe water out of just about any liquid with water in it, and it runs on anything burnable, as well as acts a power generator as well. Its completely portable and about $2K, but I can't buy it, they are all going to third world countries and being custom built...what a waste, they will be the first to go in the revolution.
http://www.esquire.com/features/dean-kamen-1208-2