[Possibly NSFW] How much of a gender bender can you find attractive?

Whether a friend or celebrity, what champion gender bender still appeals to you? If you’re normally attracted to males, how effeminate can a man get and still appeal to you? Or would you be more likely to find a very butch lesbian or preoperative transsexual woman attractive?

If you are normally attracted to females, how masculine can they look and behave and still be attractive? Or would you rather opt for a genetic male who is extremely feminine—such as a shemale or preoperative transsexual? How do you personally deal with the confusing area where the spectrum of gender intersects with that of sex?

If you know of examples in your personal life or among celebrities, please cite them. Of course, if speaking about a personal acquaintance, feel free to conceal their names and details that could be used to identify them.

Here are some technical details on the topic.