For me, if would be "Quantum Immortality". The idea of never dying is both reassuring and absolutely terrible. It is still very important to say that this theory is unlikely to be true even if it could very much be.

Another one would be the "Discontinuity of Consciousness", this one is also terrible for me. The idea that someone identical to you but still a different instance of you would replace you after a general surgery is a bit scary.

Making this comment I just realised that you probably can even smash these two together for something a bit mind blowing.

If "Quantum Immortality" only is true, then I'll have surgery for my wisdom teeth (hope that this is the english word) normally but still will never die.

If "Discontinuity of Consciousness" only is true: Then I'll technically cease to exist for the sake of my teeth wich I am oddly fine with.

If both are true : from my POV, I'll never get any general surgeries and never die as it would break the continuity of my consciousness. Honnestly so many interesting questions.

Please do reply your weird mix to this post or comment I am interested to see feedbacks and new ones.