James Harrison
Harrison was brilliant for Kent State but failed to convince NFL scouts that he had the right physique. That’s why the linebacker went undrafted in 2002 and found himself clutching at straws. Luckily, the Steelers took a chance on him and he made the opportunity count. Harrison became one of the franchise’s greatest-ever players.

The Hall of Famer was a two-time Super Bowl champion and had a crucial role in their successes. He won the 2008 Defensive Player of the Year award and was a five-time Pro Bowl selection. Many people regard him as one of the best undrafted NFL players ever because of his extraordinary story (via Men’s Journal).