Mine I think is "Mutiny in Heaven" by The Birthday Party.
I also have a fondness for "Coming up Roses" by Elliot Smith. Swie had been shooting heroin again for four weeks after almost 9 months of being addiction free, and then stopped ct. On about the fourth day of stopping she heard that song and almost cried. She'd been out that day and everywhere she went was reminding her of shooting up (it's a sad state when station toilets make you want to cry). The phrase "coming up roses" apparently refers to pulling blood into the syringe when you register (I never knew that before), and there's a line in the song, "You're coming up roses, everywhere you go." That line just captured something for her and has really meant something to Swie since then.