There are lots of dystopian movies and TV shows. And current subgenre is the zombie flick. But many dystopian movies and TV shows don't feature zombies. Examples include Gibson's Max Max series, Jericho, The Book of Eli, and Revolution.
Some dystopian films have a political agenda. During the Cold War, you had movies promoting unilateral nuclear disarmament (On the Beach; The Day After). Others have an environmentalist agenda (Soylent Green; The Day After Tomorrow).
In these films, with the destruction of civil authority, human society reverts to barbarity. You have roving rape gangs. Cannibals. Brutal, dictatorial city-states.
Some survivalists promote the gold standard, on the theory that in the event of gov't collapse, gold will become the fallback currency. But in a post-apocalyptic scenario, many things will be far more valuable than gold, viz. guns, bullets, batteries, gasoline, medicine, flashlights, lighters, pocket knives, chainsaws, solar chargers, drinking water, canned goods, women of childbearing age.
One question we might ask is what are some of the more realistic causes of a post-apocalyptic world? Likewise, what would be the greatest threats in a post-apocalyptic world?
One looming concern is whether, in the not-so-distant future, pandemics will return because the overuse of antibiotics (and antivirals) led to resistant strains. A post-antibiotic world which reverts to a pre-antibiotic world. Antibiotics are also essential in surgery to stave off infection.
Another possibility is that when scientists clone fossilized organic matter, that will accidentally release an ancient pathogen for which modern-day humans have no resistance.
Like theories about how the vastly outnumbered Conquistadors were able defeat Mesoamerican warrior cultures. Was it due to their exposure to European diseases?
Suppose most of the human race was wiped out by one of these pandemics, leaving scattered survivors. What would pose the greatest threat to survivors? In movies and TV shows, it's usually desperate fellow humans.
But here's a neglected threat: dogs. Of course, a percentage of dogs would starve to death because they can't escape the house or fenced yard after their owners die. But other dogs would be on the loose. Without owners, they'd form packs and revert to their wolfish instincts. Big dogs would eat little dogs (as well as cats). Tough dogs would kill sweet dogs. Bad news for Golden Retrievers.
You'd end up with roving packs of pit bulls, Dobermans, German Shepherds, Malinois, Tosas, Presas, Rottweilers, Irish Wolfhounds, &c. And humans would be on the menu.
Handguns and rifles might be inadequate, since you might be unable to get off enough shots to drop a vicious dog pack. You'd need a submachine gun.