I wish to be able to change my gender at will, I would need to know how to do it and control it so I don't do it accidentally though. I could change my height, body type, voice, hair color, eye color, and other important details that I would need to say beforehand to look like the kind of person I want to be. And to make things less complicated for when I would turn back to normal, I would just need to say one word or phrase.