Fandom x Reader OTP Challenge

I've done the OTP Challenge a couple of times now and I keep getting distracted from it, but this sounded really fun. Since I'm posting this on several sites, if more than one of you comment wanting the same one, I will either choose the one that would be easier to write, or I'll choose the one I see first. Fandoms include Avengers, Supernatural, Harry Potter, the Hobbit, Sherlock, and some other misc. characters.