I once met a Doctor Nurse. Imagine how fed up he must have been with all the jokes...
If people really want their child to be different, these days you are better off calling them Peter or Jane. Or John or Mary I guarantee there will be no-one in their reception class with the same name!
Mind you, I am quite pleased with the popularity of Jack. Once met a children's storyteller who pointed out that there are LOADS of Jacks in traditional British stories - more Jacks than any other name. So it's kind of honouring our traditions and culture, innit?