Sullivan is a jaunty Celtic three-syllable name, with a real twinkle in its eye. It was immortalized in the 1930s classic film Sullivan's Travels and was chosen for one of Patrick Dempsey's twin boys. Nickname Sully is equally jaunty.
The third most common surname in Ireland, Sullivan's heritage dates back to the third century. Countless distinguished surnamed-Sullivans include Sir Arthur, half of composing team Gilbert & Sullivan, Helen Keller's teacher Annie, Chicago architect Louis, early boxer John L. and dour columnist/TV emcee Ed.
Other celebs with boys named Sullivan: singer Tom Waits and actor James Marsters. Heroic pilot Chesley Sullenberger is known as Sully, and a featured character in Pixar's Monsters, Inc. is also Sulley.
Stylish and boyish but could work for a girl -- especially one with brown eyes -- though Sully is not the most appealing of nicknames.