John McEnroe
McEnroe is one of the best tennis players ever but he had a dark side. He had amazing rivalries with the top stars of his era yet he also had some infamous moments of bad sportsmanship. One of these became iconic and surprisingly enriched his career. He competed at Wimbledon in 1981 when he said the immortal phrase: “You cannot be serious.”

An umpire felt the full brunt of McEnroe’s fury after a call went against the American star. The official said that McEnroe’s shot went out but McEnroe emphatically disagreed. “You cannot be serious,” he roared. “That ball was on the line.” He attracted a lot of criticism but it became the title of his autobiography and his trademark catchphrase (via Reuters).