hands down, is "(What's so funny 'bout) Peace, Love and Understanding?", performed by Elvis Costello but actually written by Nick Lowe.
It is perfect. It has a message (the message) and lyrics that cry out from the soul. It is passionately sung by Elvis and flawlessly performed by The Attractions, who were obviously inspired by the song when they recorded it. It asks the question that every thoughtful person must ask themselves when confronted by the careless cruelty, the mendacity of the world.
It takes the driving force of punk rock and directs it squarely at society, and at the same time back at itself, at the sneering cynics and fashionistas, and drives them from the temple. Stunning, and never equalled in the pop canon of "serious" songs/songs with a message. Bless Nick Lowe, and Elvis, bless 'em.
I'm not actually drunk as I write this, although it might appear that way. This song just always puts an arrow straight through my heart.