BloodMetal is notwithstanding, as I will come up with another name hopefully. It's a mix between a sci-fi setting (Mass Effect, without the aliens or space travel), a zombie apocalypse (akin to the Walking Dead), nuclear wasteland (akin to Fallout), and life has pretty much returned to medieval-esque periods, with some guns thrown in rarely.
It takes place in a futuristic, post-apocalyptic, reverted setting. The world became technologically-advanced. Unfortunately, an airborne infection caused millions of people worldwide to turn into these flesh-eating cannibals, sort of like a zombie (although they're NOT zombies, they just seem like it). Eventually the infection was just to much, so deadly nuclear missiles were launched on the most dangerous areas, wiping out most of the infected, and the radiation killed the infectious strain.
After that the world's population was drastically reduced. Some areas of the world was entirely absent of life, most regions were inhospitable cause of radiation, and the few pockets of survivors that remained were forced to hole up in camps and try to survive in the post-apocalyptic world. These survivors were forced to go on supply runs and had to deal with deadly bandits and what was left of the infected.
That occurred over a century ago. The world's population has increased, but it's not by a substantial amount. They still live in camps scattered across the world, making do with what they have. The infected are still a problem, but not as much as they once were. Only a few communities use electricity, powered by repaired dams. Vehicles are rare, as is fuel, so horses are a main mode of transportation. While guns exist, ammunition is very sparse and used as a 'special form' of cash (as an example, the average person caries about 3 bullets). As such, mainstay weapons actually include improvised swords, axes, spears, and crossbows. Shields are also crafted and used. Armor from days past is used (imagine Clone Trooper, Stormtrooper, N7 Armor, that kind of stuff, but it's damaged, scratched, and pieced together) in combat as well.
Commons - Commons is the term given to the simple, common, average people who live in the communities. They support themselves, stand up for each other, and try to live normal lifes.
Nomads - Loners and roamers out on the roads, who may or may not stop at Communities they run across. Most just like the nomadic lifestyle, some are bounty hunters and mercenaries, others are just crazy psychopaths.
Vandals - Vandals are like Commons, but they ambush and raid others on the road, leading a life of banditry.
Infected - The infected are cannibalistic humans. Weak and slow, they're not as much as a problem as they once were, especially since the airborne strain has been killed by radiation (although being bitten is still contactable). But one should never underestimate them in large numbers!
The typical adventurer might wear some clothes, and will pick up and equip pieces of armor he may find. They may carry a firearm, such as a pistol, rifle, or shotgun, but ammo is extremely sparse and so melee weapons are generally used. As such, the average adventurer might use swords, shields, and crossbows. Ammo is used as currency in most locations.