Freakin' incredible!
The gameplay was amazing, the choice of weapons was great [My favorite combo was the Barett and the chainsaw.], the variations in the zombie was great [ie: the swat and soldier with the body armor], the sound was incredible.
Now for the things I didn't like too much. I agree with JimmyDimples about the sleep thing. It's an interesting concept that could make the game even better than it already is. Maybe a limited amount of clips and when you ran out you had plenty of projectiles [ie: molotov cocktails, grenades, javelins, bow and arrow]. I'll definitely be looking for a sequel maybe, and it would be amazingly hilarious if you did put the javelin in. Oh, man. I'd love to be able to pierce a zombie with that.
Setting should be in other places. Other than all of those things I mentioned, this was the best game I have played in years. Not just on Newgrounds, but anywhere.