I've got several sets of rules. My current kick is building post-apoc terrain for Skank or, if Wreck-Age would ever release, that. Maybe Nuclear Renaissance.
My biggest thing is a fun, silly-ish, simple skirmish game set in a "post-apoc nuclear/bio death" time where scenarios can be very wide-ranging, from protecting the installation (read: Road Warrior) without vehicle combat. Simple = I can get people to play it.