Thats intense! pill poppin' shotgun totin' action! has the same sort of appeal as some mausland shooters so thats always good :D I'd say the controls might need refining as i couldn't move down and shoot at the same time, but that might just be my sucky keyboard.
To improve, i'd say clean up the drawings a bit and the interface to make it look less like it was done in MS paint (is it?). Zombies must have elaborate gore, i think that should be made law, i'd like to see it in future versions!
Good job tho :D