think about this, though. With all the zombie chopping you'll be doing, the blade is gonna get real dull. Soon you'll be left with a blunt metal weight, and that's not very useful in zombie smashing at all.
I like that one poster's idea of a flame thrower, problem is, burn=/=death. Most things that burn can still move while burning, which makes me think it wouldn't be the best weapon of choice.
A gun is only as good as the marksmanship of the user, and personally, my aim is horrible.
I pick a totally tricked out school bus, with huge razors protruding from the frame on both sides, a big cow-mover-type-dealy like you see on the front of old trains, only outfitted with spikes and more blades. The tires are wrapped up in heavy metal chains, to make crushing zombies an easier task.The glass is reinforced with iron bars, to prevent any zombies from getting through in case the glass breaks. In the back of the buss is a flamethrower, a sniper rifle, and a machine gun, and several hundred pounds of ammo/gas for use by a gunman who pops out of the emergency exit on the roof.