As I'm working on the homepage, I came across a great article on Harrison Dillard's 1948 men's 100 gold medal being on auction. The guy was the best hurdler in the world (he'd win Olympic gold in 1952) heading into the 1948 US Trials and had won 82 hurdle race sin a row but he didn't make the team in the hurdles. He squeaked on to the 100m team and then won that.
In 1952, he didn't defend his 100m crown as he wanted his hurdle gold (which he got).