The multiverse theory, in case you're unfamiliar, says that each time there are different ways a quantum event could go, the universe splits into multiple universes, one in which it went each way. There is an extension to this in which free will is manifested by your consciousness following a given universe in each split.

This has the strange consequence that only you have free will, as perceived by your own consciousness. I don't think this makes any less sense than anything else related to quantum physics, but it is definitely weird.