Ohh, I had an interesting thought one day, but I have a feeling it's already been used.
It's an RPG sandbox that takes place in an abandoned suburb. It is a single player game, and the main character has some sort of disorder, where he views everything as perfect, when it is really not. He believes he is in a suburb a la Edward Scissorhands, yet he is really in a supernatural, monster infested hell hole. In his eyes, the NPC's are normal, happy go lucky people, but in reality, they are rotting corpses.
BUT, the catch is that he can see the monsters. So, in his eyes, he is in a perfect, spreawling, colorful, sunny suburb... filled with flesh eating monsters. Mindfuck much?
As for the story itself, I haven't really come up with one, to be honest. It could be something along the lines of him believing that he is uncovering some sinister plot in the making, yet the player knows that he is really uncovering the events that have already happened to the place to make it the dark, awful place that it is.
While the player will probably realize that the main character is uncovering evidence to prove what has already happened (The destruction of the suburb) it will be like seeing the end of the game at the beginning.
I have no idea how this game could be presented, as the player must know the true nature of the suburb, while the main character cannot, but it would certainly present a challenge to a game designer, I am sure.
And is something out there, some unknown entity playing God, controlling the events as if it were a mere plaything?
I have no idea.
But it sounded good in my head.