Sam's scar

This scar on Sam's palm helps him decide what is real and what isn't. Using the pain, Sam can snap out of hallucinations, and come back to reality. This plays a subtle part in Sam's life in Season 7.

History
Sam first cut open the hand in Meet The New Boss when he remembers hell, and falls on glass. So his hand is bandaged up. In Hello, Cruel World Dean shows Sam how to use the pain from the scar to figure out what is real and what isn't. This is because pain in hell is different from pain in rel life. With this knowledge, Sam uses the pain from it to get rid of his hallucination of Lucifer.

This seems to work for Sam so far. After the accident with the Leviathans, Sam zones out only once (The Girl Next Door), but is soon brought back by the pain from the scar.

Used

 * Hello, Cruel World
 * The Girl Next Door
 * Defending Your Life

Trivia
At a convention, Jared and Jensen commented on how Sam and Dean get bashed up but always heal. But this time with Sam's hand it didn't. They comment on how they had a joke about CW cream that healed everything, but it looks like they ran out.