in "Starship Troopers" the soldiers fire mini-nukes (still not sure how that works). A nuclear war doesn't mean BOTH sides have nukes, just one side uses them
Wasn't released in theatres but in "Animatrix", the two shorts (The Second Renaissance Parts I & II) on how the machines took over has the humans using nuclear weapons in a war against the machines.
If you want to get picky (or not), in Terminator 2, Sara has a dream about the start of the machine attack in which they nuke LA (there wasn't an official "war" but more of a pre-emptive strike)/
Aliens: Yeah, I KNOW there's no war, but the tagline for the movie is "This time, it's war" AND the nuke plant reactor does go boom a few minutes before the movie ends (picky picky picky, eh?
Wasn't there a "Twilight Zone" in which a librarian wishes he would be alone, then nuclear war happens & he is alone (and he breaks his glasses)?
If we made a list of movies that are based around the aftermath of nuclear war, i think we'd have a better list.