Ive come up with tons of them, and I want to read some of what other people have come up with.
One of my games is an RPG, its very similar to Kingdom Hearts(gameplay and story), except, it has a modern present day setting like Pokemon and Earthbound(Mother). The main character has a weapon similar to a keyblade, becuase it also fires beams of light to unlock gateways.
Another one is like Sonic the Hedgehog, except the main character is slow moving, very nonchalant about time(he'll get there when he gets there), he can manipulate time and has wings. it has the style of modern Sonic games(like Sonic Unleashed and Sonic Colors).
And another one is similar to Pokemon(with same setting), but the creatures can be ANYTHING: furniture, houses, food, cars, and animals as well; literally anything!
All the time! I've thought of one that's open world and you fight with your guardian (spirits if you will) by your side. It's really cool when it plays out in my mind. I've named it ''Guardians Of Heaven''.