Apocalypse World is a storytelling game by Lumpley Games, set in a world gone wrong.
From the back cover pitch:
Something's wrong with the world and I don't know what it is.
It used to be better, of course it did. In the golden age of legend, when there was enough to eat and enough hope, when there was one nation under god and people could lift their eyes and see beyond the horizon, beyond the day. Children were born happy and grew up rich.
Now that's not what we've got. Now we've got this. Hardholders stand against the screaming elements and all comers, keeping safe as many as they can. Angels and savvyheads run constant battle against there's not enough and bullets fly and everything breaks. Hocuses gather people around them, and are they protectors, saviors, visionaries, or just wishful thinkers? Choppers, gunluggers and battlebabes carve out what they can and defend it with blood and bullets. Drivers and operators search and scavenge, looking for that opportunity, that one perfect chance. Skinners remember beauty, or invent beauty anew, cup it in their hands and whisper come and see, and don't worry now about what it will cost you. And brainers, oh, brainers see what none of the rest of us will: the world's psychic maelstrom, the terrible desperation and hate pressing in at the edge of all perception, it is the world now.
And you, who are you? This is what we've got, yes. What are you going to make of it?
The game uses a 2d6 resolution system powered by the story prompts of you succeeded, you succeeded, but, and something else happens. It is driven by the players- the characters they play fit into archetypes referred to as playbooks, each unique, but intertwined, with their own moves that put the fiction into the players' hands- the moves follow the fiction, not the other way around.
An active community exists, both on the official forums, and elsewhere on the web, and hacks- derivatives using the rules in new and interesting ways- are actively encouraged and supported.
Use this tag when referring to Apocalypse World proper- but also to draw attention to hacks if related to the mechanics of the game.