39. Marianne Vos
Cycling
Netherlands
Age: 21
Vos has won virtually all the Dutch, European and world prizes available to road, cross and track cyclists — except an Olympic medal. That shouldn't be a problem. A prodigy who started racing at five years old, she would later cycle 24km each way to school as her daily warm-up before training. In her first season as a senior racer, at age 18, Vos became the youngest ever world cyclo-cross champion, adding the world road title shortly after. Effectively self-coached, the unassuming 21-year-old is still studying biomedical science and says she sees cycling as "a big hobby." Don't believe it. "She's a killer," says Dutch team coach Johan Lammerts. "She just has to see the finishing line and there is no stopping her."