James Doohan (Scotty on Star Trek) lost the middle finger on his right hand during the Normandy invasion. He's a genuine hero. On screen, he usually keeps the hand out of sight or clenched in a fist. There are a few frames where the missing finger is obvious, such as the frame below from the episode titled "Who Mourns for Adonais?" Scotty rushes to protect a crewmate, and exposes his right hand in the process.