9. Devil's Trap
Unlike most shows, Supernatural has nailed just about each and every one of its season finales, but few have matched the sheer intensity of the series' first, Devil's Trap. Having spent all season searching for their missing father, John, and trying to understand more about the demon that killed their mother, Sam and Dean finally come face to face with the entity that's caused them so much pain. Unfortunately for them, it just so happens to be currently possessing their dad.
The entire episode is an adrenaline rush, introducing Bobby for the first time, the concept of the titular devil's trap and exorcising Meg, but it's the final confrontation between Dean, Sam and a possessed John that summed up what everybody loved so much about this early season.
All the actors bring their A-game, but it's Jeffrey Dean Morgan's turn as old yellow eyes that proved just how much he had to offer the industry. Watching him tear Dean down verbally was almost as heartbreaking as watching the demon tear him down physically. Still, their exchange had nothing on John, retaking control of his body for a brief moment, telling Sam to "shoot me in the heart, son" in order to vanquish the evil inside.