I’m going to take liberties with this and add somethings that are maybe more dystopic than post-apocalyptic, but really they are almost the same thing.
I know Logan’s Run, The Omega Man, Tank Girl, Last Night (1998) and The Road should be on here, but I haven’t seen them so I can’t recommend them other than to say that I myself need to watch them, so you should too. You might also argue that the Alien series is dystopic. And probably the Terminator movies as well, though I haven’t seen the latest one. I am probably missing some things because I’ve only had one cup of coffee so far this morning.