Just before I left, I bleached my hair. When it started growing back out, I decided to try dying it black, and then it went purple.
Needless to say, the principal at my school was not pleased with this development, and he personally took me to the barber's to go and have my head shaved. And this was in the middle of winter, too, so I was a very cold teenager for a while
Other than that, no major bodily modifications to speak of. I think the greatest changes that have happened to me have been internal, not external.