Serena Williams

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Serena Williams

Power 100 rank: 16
Sport: WTA Tennis
Age: 28
Most recent notable achievement: Ranked No. 1
Earnings: $11.5 million
Key sponsors: Nike, Kraft, Proctor & Gamble

Why she's on the list: In 2009, Serena could do no wrong. She returned to the top of the world tennis rankings, and her expletive-ridden U.S. Open outburst apparently even netted her an endorsement deal with Tampax.