Audra Mae - Forever Young
Music can make or break or show for me, I mean who knows if I would have completely fallen for Supernatural without the amazing music in the first couple of seasons? But this song, used at the beginning and the end of "The Sleep of Babies" was used so well. The exact same song, used with a montage of the same characters both times, only the circumstances at the end were the complete opposites from the opening. The song reinforced the uplifting and peaceful opening shots, but at the end, it only added to the despair the characters were feeling.
Anyway, in a word, it was COOL. So, there you go.