As others have said, permanent full body hair removal, although I would keep the hair on my head.
Severing of the nerves that control the external bladder and anal sphincters. (These nerves aren't developed in babies and toddlers, hence why they have no control.)
Gender reassignment so I would be a girl.
And in the realm of fantasy...have my height reduced to about 90cm and weight to about 15 kilograms.