I'd go for bioluminescence over photosynthesis. Especially if I could control it. I would totally be a hit at the clubs if I could make my body glow to the music.
I think Darth has been reading too many of those ESL spam posts.
I'd like to be able to chance skin pigmentation too, like octopi or chameleons canm. Not to crazy degrees like in comic books where people can 'disappear" by blending into the background, but just to be able to change my appearance at will.
I would like to change pigmentation too, although it would be to actually look tanned. I have to get freckles before I even begin to get dark. Of course that would also take away skin-based racism.