The new first person shooter game, RAGE by id Software has an interesting back story, from Wikipedia...
The game is set in a post-apocalyptic wasteland created by an asteroid impact, based on the real life asteroid Apophis, which is on track to pass near Earth in 2036. In Rage's story, the asteroid hits, and the few pockets of survivors are forced to start a new civilization.
From the RAGE game site...
August 23, 2037: Apophis 99942 strikes the eastern hemisphere.
Carrying the force of 2.4 million megatons, 30% of life on Earth becomes extinct in 26 seconds.
Within one year 80% of all life is gone. To make matters worse, Apophis contained large amounts of heavy elements. Darkness blankets the planet. The Earth falls into an impact winter lasting almost 50 years and life on the surface is driven to the brink.
Prior to impact, in an effort to save human civilization, Arks are constructed and buried deep underground. These cryogenic lifeboats carry humanity's future, preserved with the tools they need to rebuild. They are the seeds of Earth's rebirth.
But when survivors begin to emerge from the Arks, they find the unexpected. Many humans who were above ground during the impact unexpectedly survived, while horrific mutants roam the dead cities. And a mysterious tyrannical government, bent on creating a new world order, has begun the search . . . for you.
Link: Wikipedia (http://en.wikipedia.org/wiki/Rage_(video_game))
Link: RAGE game site (id Software)
