Cataclysm: Dark Days ahead is basically a freely distributed and still being worked on Rogue Like horror RPG. It have the learning Curve and the fun of Dwarf Fortress and there are plenty of ways to die. I highly recommand Rycon Roleplay's lets plays of the game to get an idea of how its played. But basically the plot is this...not only has the world ended but pretty much a crap ton of different world ending events happened...all at once.
Zombies, check
Eldritch horrors coming into our world, check
Mutated Plants who want us dead, check
Mutated Fungi who want to assimilate us all, check
Many more things going on, this fanfiction is basically my idea of a one shot survivor and dealing with the events in a what if AU.