A Boy and His Dog-
Life in the post-apoc and you've got vaults and the problem of vaults. Note that the Vault problem is similar to one found in Fallout 2 in a rather similar society. The consequences of the biological imperative after nuclear holocaust. Plus Don Jonson is the intellectual inferior of his dog. Did I say it has vaults? Oh it also has a scav village not unlike Junktown.
Oh yeah, and remember that crappy porn they were showing? lol!
The Omega Man-
Charlton Heston, republican conservative and future NRA president, gets it on with a hot black chick. Does he kill her when he finds out she's become a monster? If you can handle it, also try Last Man on Earth- similar story, but if you want more, read Matheson's I Am Legend- form which these stories derive.
Oh yeah, I forgot about Last Man on Earth, that movie was closer to the book. And Vincent Price was closer to the book Robert Neville.
Also, here are some more PA movies:
Beneath Planet of the Apes (1970): Not as good as POTA, but it does have telepathic mutants living in an underground vault. And it has a cool ending too.
Battle for Planet of the Apes (1973): Pretty stupid, but it does have a good PA mutant vs. ape battle at the end. Very low bugent and crappy, but good for cheeze lovers.
Zardoz (1974): This movie is too strange for words. It does have a group of immortals living in an enclosed area after a nuclear (?) war. It also has Sean Connery running around in an orange diaper and ammo bandoliers. And a guy who wears underwear on his head and has a drawn on moustach. And a giant flying stone head that hates penises and vomits guns. They don't make movies like this anymore . . . I wonder why . . .
Logan's Run (1976): Takes place in a vault-city-esque place (actually, a dome, IIRC) where no one is allowed to live past 30. Pretty cool movie, and Jenny Agutter is hot.
The Day After (1983): Shows the aftermath of a nuclear strike from a town in Kansas' POV. Grim and depressing, but not as much as Threads.