Wasteland 2. Very fun. Harkens back to the old. Or play Fallout 2. Or New Vegas, for those not into the old stuff. Watch Mad Max II.
Remember, too, that post-apocalyptic does not necessarily mean that some sort of nuclear weapon annihilated everyone. There could have been a superflu (more likely), or some sort of Judeo-Christian uprising, complete with hooded nihilists bent upon the catechism of the gun.
Et cetera.