Post apocalyptic RPG/FPS. Not like Fallout or Borderlands, I mean realistic settings, like what would happen to the world if there was a bunch of EMPs going off or if we all ran out of oil. Game play elements would have some regular FPS stuff but how accurate you are will be based on your ballistics skill, how far you can sprint will be endurance, making weapons would be a combination of intelligence and mechanics skill or something. And the enemies would react to bullets like in Red Dead Redemption, except when you shoot them in the face with a high caliber weapon their skull structure reacts realistically. Also, the game would be severely realistic. Like, if you reload a magazine and there is still bullets in your last one, you pretty much wasted them. You have to zero in your scope for rifles.
Not only that, but you can make a weapon out of anything when you're in a pinch. Rip a leg off a chair, pick up a screwdriver and jam into into someones eye, grab a beer bottle to bash it across someones face. This game sounds awesome.