Thanks for the feedback and contributions, esp. to Error014!

I don't think anyone should or would simply do a game directly based on one idea presented here, instead I think this thread could be seen as an inspiration for own game ideas.
A simple character or a style as inspiration 2) in my first post here can be enough to lead you to a great game, I think when you see such a thing the whole game can unfold in your mind in seconds. As I've stated in my OP I don't think a game needs or even should have a unique mechanic, that's why I encourage other users to post inspiring images as well.