Ernest Hemmingway
Before he was one of the most iconic writers of modern history, Ernest Hemmingway was a young teen hoping to enlist in World War I. However, once it was revealed that he had terrible vision, he was denied from participation. He managed to help by becoming an ambulance driver. Doesn't seem like a driver should have terrible eyesight, but it apparently worked out well...
Humphrey Bogart
Humphrey Bogart might seem like he was born for the silver screen, but once upon a time, he was in the US Navy police. While serving as part of the US Navy military police, Bogart was accidentally struck in the mouth by an unknown object. This attack gave the future actor a tiny scar above his lip and contributed to a minor lisp that added to his tough image in his career.