A couple of years ago a friend got to work and heard a sound. There was a kitten hiding under the hood of her car. It was so timid, it spent the day sitting on her shoulder, hiding under her hair. She really didn't want another animal but couldn't find it a home so it joined her other cat and dog.
Within a year, the kitten had been nicknamed "Satan." The other animals (including the puppy that since followed my friend home from the park and now weight 70 pounds) are scared of it. My friend isn't scared but, if she doesn't get her way, the cat plots revenge and destroys things.
Overall, I'd say my friend did an excellent job building Satan's confidence and getting her over her timidity.