17. Britney Spears – Nail Biting
Britney Spears has been dealing with a habit that many people find very hard to break, but it is not something you would usually expect from a celebrity. The former teen popstar has admitted to biting her nails until they were not only short and stubby, but bleeding as well. There are even photographs of her with very bloody fingertips showing that she has yet to break this bad habit.