Well I was not expecting that much of a turnout from my post last night! lol 74 comments so far. Amazing! It was great hearing from so many of you. It's cool to know why a particular transformation appeals to you.
Anybody TG asked me what MY favorite was so I suppose it's only fair I tell you all, though I think it's pretty obvious ;) Body Swaps are my all time favorite. Like some of you mentioned, it's more interesting to me to have two people caught up in a situation together. Sometimes I like when they hide it and pretend to be each other but I also love when a few close friends and family are in on it. It's always been fascinating to me ever since I saw all those body swap movies from the 80's. lol I have a soft spot for the ol Mad Scientist brain swap machine. I think that stemmed from the Gilligan's Island episode if I remember correctly. Also, as it's probably obviously, I like there to be an age difference between the swaps. Adults to teens and vice versa. Something like the husband/wife or boyfriend/girlfriend is find less appealing because they are already familiar with their lover's body. It's still appealing to me but less exciting.
Possession and shapeshifting are great as well but like others had mentioned it feels morally wrong taking over someone and them not having any control over it. Same with costume gun. It's a cool idea but in real life it'd be pretty fucked up lol
Thanks again everyone for your answers. It's cool to hear what everyone had to say :)