#9 Has never retired from a match
Roger Federer has had a long career in tennis and has so far, as per Wikipedia, played a total of 1358 singles matches, holding a win-loss record of 1111-247.
The recently concluded Wimbledon saw his close rival, Novak Djokovic retire from the tournament due to an elbow injury and also saw his other adversaries, Andy Murray and Marin Cilic struggle with injury problems.
An astounding stat of Federer's career is that he has never retired from a tennis match, and has proceeded to complete every match that he has begun. This bears testimony to the fact that one has to have single-minded dedication and mental strength to succeed, apart from talent.
#10 Vegetarian till the age of 14
Growing up in Switzerland, Roger Federer was a vegetarian by choice, and decided not to eat meat, a decision that was supported by his family.
Federer then moved to a tennis camp at the age of 14 and had to eat non-vegetarian food as prescribed by the institute, so that he could develop well physically.
Who Are Roger Federer's Kids? Know All About Federer's Twins