Zombies Attack is my zombie survival pocket RPG, and the Zombies Attack Skirmish rules let you play out miniature based combat scenarios quick and deadly.
You can download the skirmish rules, or go wild and download the rpg and its supplement and the skirmish rules all at one time! Find them all on my Zombies Attack blog.
If there is enough interest I think an OPFOR (modern military vs terrorist) spin on the rules could be next, or maybe more ZA Skirmish scenarios? Who knows what fevered ideas may breakout next.
I recommend Rebel Minis as a great source for quality 15mm figures to use.