I guess it depends on what you'd call "fetish".
The thing that really gets me going, if no one has guessed, is personality changes. There's a lot of stuff that kind of go hand-in-hand with that, like reality changes, mind control, lifestyle changes, sexual orientation changes, etc. And none of those concepts require any type of sexual narrative (even that last one, as the characters could just be kissing or showing romantic affection for each other).
