I’m working on a game about characters surviving/dying in the end of the world. The setting is a dark fantasy world (elves, dwarves, orcs, fighters, wizards, etc). I’m using the Crew mechanics for the Apocalypse (it has a Tier rating, special abilities, reacts to what the characters do, etc), and groups can choose what kind of Apocalypse to play through (world war, plague, demonic invasion, for example).
The mechanics are intended to drive characters to have conflict with other characters as they pursue their goals. One example: instead of an assist move to assist another character, characters can get extra dice for their action for free, but all complications of their move are visited on the other characters instead of the acting character. They accomplish what they wanted, but others suffer (like securing the door before the horde gets there, but some people are trapped outside). And if their selfish move failed? That’s a great opportunity for a hard GM move that drives home the horror of their actions. The game is about seeing how far characters will to survive and facing the costs of that survival.