(Spoilers Main) What is the best theory you've ever read?

What are some of the best theories/best theory you've read?

One of the theories i enjoyed the most was about the one where the heart of winter is actually a weirwood tree in the far north... with an "evil" greenseer (a COTF) bound to it. This entity is controlling the white walkers. That was what Bran saw in his vision/dream when falling down.

https://www.reddit.com/r/asoiaf/comments/angoio/spoilers_extended_the_heart_of_winter_fell/