With such a dark and depressing episode and Dean seeing the disastrous outcome of things of a future he must prevent, I think seeing him returning to the present and realizing how much he values his friendship and companionship with Castiel as he is just makes my heart swell. It's something about Dean seeing Castiel as the angel who sacrificed so much, who is with him the entire time fighting side-by-side with him, and acknowledges and appreciates this fact by telling Castiel, "don't ever change." This is something that Dean rarely does to anyone, and the fact that he did it in this scene is amazing. I just, I cannot fathom how many times I have watched that scene and it made me smile like a loon. I can't help it. ♥
Seriously, just look at the way they're looking at each other. *draws hearts all around them*
Runner up is "A Very Supernatural Christmas" because first of all, it was a Christmas episode and I'm a sucker for those. Second, it featured flashbacks to wee!chesters and that was so touching, giving more light to the brotherly relationship between Sam and Dean and, of course, that heartwarming ending. Showing that you don't need some huge show to express the holiday spirit. Newspaper-wrapped convenience store bought presents and homemade eggnog will is all it takes, especially if you're spending it with people you love and care about. :)
Rest of the 30 Days of Supernatural Challenge.