2. "Run." (Season 3, Episode 12)
This was the ending to the penultimate episode of season three and it was a damn good set-up for a season finale. Earlier in the series, Jesse had come to learn that a couple of Gus's men were using children to sell drugs. He took issue with this, mainly because it was his girlfriend's little brother who had been sucked into doing it. When Gus eventually decides to tell the two men that they can't use kids, the two men saw fit to kill the boy. Jesse decided to do what any sane person would do; stake out where they sell meth and plan to murder them. He quickly knocks back a bit of meth beforehand for some Dutch courage and steps out of the car, walking towards where the two men have parked up. The two step out to face Jesse and the shoot out is on. That is until Walt comes bursting in, absolutely mowing the two of them down with his car. One is completely crushed by the car, the other is barely alive on the ground. Walt grabs the gun of the survivor and double taps him, just to make sure. After this heroic moment of absolute bad-assery, he simply looks up and says one word: "Run." Even watching the clip back now I can't help but smile at how unbelievably good this moment is. It's the slow build up from the moment Walt is in his house trying to call Jesse, only to be met with no response, to him spotting the news report, to Jesse walking out. Walt leaves his house and we don't know where he's gone, we have no idea he's about to come in and save Jesse's life while risking his own. It's the shock value as well that adds to the impact. You're watching two pretty realistic looking people getting bowled over by a car, the sheer unexpected nature of that alone is enough to make the scene great. The way Walt says "Run" is chilling, as he's fully in the Heisenberg zone at this point. It is the perfect penultimate episode to a season.