Andre Agassi

Andre Agassi won eight Grand Slam titles and completed the Career Grand Slam, but his financial legacy is built as much on his brand as his backhand. His Nike endorsement deal was among the most valuable in tennis during the 1990s, and his flashy style -- denim shorts, long hair, and earrings -- made him the sport's most recognizable crossover star. Additional endorsements with Canon, Mountain Dew, and Head generated millions annually.

Agassi's post-career wealth has been driven by real estate investments in Las Vegas and his marriage to Steffi Graf, another Grand Slam champion whose own endorsement and business income added to their combined family wealth. Together, Agassi and Graf are arguably the wealthiest couple in tennis history. Agassi also founded the Andre Agassi College Preparatory Academy in Las Vegas, a charter school for underprivileged children that has become one of the highest-performing charter schools in Nevada.

His autobiography, 'Open,' published in 2009, is considered one of the greatest sports books ever written and revealed that he secretly hated tennis for much of his career, wore a hairpiece during his playing days, and used crystal meth. Despite these revelations, his commercial value barely dipped -- a testament to the authenticity of his public redemption narrative.