Ivo Heuberger and Martina Hingis

It's because of relationships like the one she had with Ivo Heuberger that Martina Hingis received the nickname "the black widow." After competing together in The Hopman Cup in 1999, the two had a summer romance. Heuberger, who was the No. 2 ranked player in Switzerland at the time, finished the year at No. 4 in the country. His overall ranking dropped from No. 125 at the beginning of the year to No. 219 at the season's end.