I think i have a good idea, try to make it possible to attack cities, (people dont randomly drop from above) reg. people will have rank 1 guns (sometimes), police rank 2, SWAT rank 3, and army rank 4. There could also be some kind of upgrading system, and you can buy guns for yourself, (Loads of money and you have to buy ammo) plus you start out with REALLY bad accuracy.
P.S. The idea of having too many zombies that you die is a good idea.
Has a good potential, but should maybe have a customizable character at the start, and whenever you get caught by cameras or something like that, you have the chance to run as cops chase you. (with more flat terrains and a very small amount of things to jump over. And if your right behind a cop, they can hear you and turn around. But still about 5546794753% better than any crap i could come with.
I googled "Chuck Norris getting his ass kicked" and my last laptop crashed. It could've been a coincidence.....but probably not.
For the record, I'm SERIOUS, it really did crash soon after i pressed enter.