Hard to pick just one ... so I'll provide several choices.
Choice #1: "re: Stacks" by Bon Iver.
I've already posted about it on my other blog, but Pop Rocks wouldn't be complete without some Bon Iver. A gentle man. A gentle song. It's the #2 most frequently played song on my laptop. This song is sympathetic and comforting. If I need to cry, it works. If I'm done crying, it works. It's atmospheric and beautifully layered. It's poignant and delicate. Beautifully delicate and delicately beautiful.