Zombie Outbreak Simulator uses Google Maps to simulate a zombie invasion in Washington DC. Some civilians are armed, and there are some police wandering around, too. My main problem with the whole thing is that the zombies and humans seem to wander aimlessly at about the same rate, regardless of whether they're being chased or not, and people who go into houses often seem to have the zombies follow them right inside, or just come straight out again themselves, rather than, say, closing the door and sitting tight for a while.
Even when I tried to weight the numbers in favour of the humans (more police, who are inexplicably limited to a total of 8, slower zombies and fewer of them) they inevitably gained a foothold and slowly but surely overpowered the population. Three hours later, all the police were still alive and the zombies outnumbered the humans. The final score several hours later: 81 surviving civilians (including all 8 police), zero zombies, 5939 dead civilians (some revived as zombies and killed again).
Mokalus of Borg
PS - The lesson here is obviously to stay behind the police when the zombies come.
PPS - I wish it kept records you could graph over time of the results.