Justine Henin

Henin won seven Grand Slam titles and reached world No. 1 with a one-handed backhand, at a time when the two-hander had taken over the women's game and most coaches would have told her to switch. She retired voluntarily in May 2008 while ranked No. 1, weeks before a French Open she was favourite to win, came back in 2010, and retired for good in 2011 because of an elbow injury. For anyone who cares about this shot, she's the most important player in WTA history, and she rarely gets talked about that way.