Nuclear war, zombie outbreaks, meteor strikes, economic collapse, alien invasion, no matter how it happens an apocalypse makes for a unique and engaging setting to run a campaign in, even for a jaded GM.
Here’s a few quick tips that can make a good zombie or other post apocalypse game a great one, and keep the group coming back (from the dead?) for more.
A great treasure has been stolen from the Palace and taken to the nearby Temple to the Bitch-Goddess Atrath Klee. The King demands that the party go and retrieve it - the only snag is that the Temple is guarded by potent magic that will kill any male who steps inside. It's just as well that the King has a stash of Girdles of Gender Alteration for just this circumstance.