I think my favourite Olympian is from the Winter Olympics, Steven Bradbury. In 2002 he won Australia a most unlikely first gold medal ever in the Winter Olympics (in fact, the first for the entire southern hemisphere) in the men's 1,000 metres speed skating. If I may let Wikipedia tell the story:
In the quarter-finals, Bradbury thought himself eliminated. He finished third (only the top two advance), but Marc Gagnon was disqualified, thus allowing Bradbury to advance to the semi-finals.
In his semi-final, Bradbury was in last place, well off the pace of the medal favourites. However, three of the other competitors in the semi-final crashed into each other, paving the way for him to take second place and thus allowing him through to the final.
Again well off the pace in the final, once more all four of Bradbury's competitors (Apolo Ohno, Ahn Hyun-Soo, Li Jiajun and Mathieu Turcotte) crashed out at the final corner, leaving a shocked Bradbury to take the gold medal, the first for Australia or any southern hemisphere country in an Olympic Winter Games event. (Alisa Camplin also won gold for Australia at the same Olympics).
In other Olympic news, Australia has won another gold, in the men's pole vault! Without injury, as opposed to the Sydney Vault of Terror. It's our twelfth of these games, but the first we actually won wholly on dry land; and our first field gold medal in sixty years.