Me and some friends used to run a RPG called The Third Wave. The premise was that a biological weapon mutated and the resulting plague wiped out everyone over the age of 20. Then, just as the rag-tag survivors were pulling civilization back together, the plague hit again… 20 years later.
The plague strikes every 20 years, killing everyone over the age of 20. These are called Waves, which have struck three times, hence the title. The setting was a post-apocalyptic New York City run by street gangs. There were three major gangs in the city to start with: *Genocide *(based in Penn Station), *Remorse *(based in the New York Public Library), and *Query *(based in the Toys R Us in Times Square). Later on *Remorse *dissolved after the suicide of their gang’s Boss, and a new gang arose, called *Desolation *(based in the Empire State Building). Even later another gang broke off from Genocide, called Exodus, which operated in secret as a splinter-cell.
We put a lot of work into the background of this future-primitive world, with the gangs having their own intricate histories, initiations, and rules. Staten Island was home to a roving band of pirates who would ravage the coastline, too powerful for even the gangs to stop. There was also the Night Thief Guild, based out of a Starbucks, which functioned as a cross between the Mafia and a police force. A massively overgrown Central Park provided a wild, tangled oasis in the midst of the urban decay.
Unfortunately, the game was never able to attract enough players to survive. We stumbled along for a year before finally closing the book on The Third Wave. There was some talk of starting another permutation, possibly to be set in Los Angeles or New Orleans, so who knows? There’s always The Fourth Wave.