What is the most famous quarter horse sire?

Well... Go Man Go was only half Quarter Horse (The other half being Thoroughbred), but he was a pretty famous horse. He did Flat racing and was named World Champion Quarter Running Horse three times in a row, one of only two horses to achieve that distinction.
During his five years of competition before he was retired from racing in 1960, he had 27 wins and brought earning of more than 86,000.