Maria Sharapova (Tennis)
Carrying the Russian flag on her Olympic debut, Sharapova has won each of tennis' four Grand Slam tournaments.
Novak Djokovic (Tennis)
The world No 1 until recently, Djokovic has won five Grand Slams, is a three-time Australian Open champion, and won the men's bronze at the 2008 Olympics.
Caster Semenya (Athletics)
Following her women's 800m win at the 2009 World Championships, Semenya's gender was subject to scrutiny and testing from the IAAF. She was cleared to run in 2010 and won silver in the women's 800m at the 2011 Worlds.