Warren Moon
Moon was another future Hall of Famer who went undrafted. The quarterback refused to allow this disappointment to define him and went up North to the CFL. There he won five Grey Cups with Edmonton and became a Canadian football icon. The Oilers decided to bring him home to the States and he became an NFL legend.

He won the NFL Offensive Player of the Year award in 1990 and was a passing yardage machine. The nine-time Pro Bowler was one of the best pure passers of his generation and kept the Oilers in contention. Houston never saw a quarterback like him before and he broke most of their records before joining the Vikings (via Andscape).