I once tried making an endless runner kind of game where the player is always moving in one direction and you can't control him, but you control the camera. Whenever player reaches a side of the viewport ( the camera ) he will enter from the other side. And you have to use this mechanic cleverly to avoid spikes and obstacles and at the same time keep the player inside your area of vision.
I left this project haf completed because of some personal problems and never got around to completing it, and now I've kinda lost the interest in the game, but still think it's a cool idea. So maybe someone else can use it.
If you're planning on making a game with a similar mechanic, I'd LOVE to play it.