In my search for famous people with three nipples, I present for your edification the curious case of Anne Boleyn, former Queen of England.
First of all, I should address the case of Elizabeth I. Although at least one report attributes an extra nipple to this queen, I think someone has got their facts confused. They were no doubt thinking of the beheaded wife of Henry VIII.
As for Anne, numerous sources say she had not only an extra nipple, but an extra finger too. If you devoured The Book of Lists as I did as a fascinated seven year old, then you remember that fact. However, this seems to me a fabrication too. Apparently, she was beheaded for incest and adultery (generally seen as excuses for Henry to marry Anne's maid, Jane Seymour) and it wasn't until about 50 years later that a biographer first made the claims about the nipple and the finger. The rumours persist and frankly, they make a good story.
Too bad about the nipple, though. I bet if she had one, she wouldn't have lost her head.