With Paul and Heather splitting, I find myself thinking about breaking-up songs. Personally, I've always gotten a kick out of the "we're splitting up and now I hate your guts" genre. My personal favorites are:
"Dead Flowers" -- Rolling Stones. For some reason FTD never adopted "Say it with dead flowers" as a slogan. Pity.
"Yes I Guess They Ought to Name a Drink After You" -- John Prine. After he sings the title phrase, he grumbles, "Bloody Mary!" How can you not love that?
"I am an anti-imperialist. I am opposed to having the eagle put its talons on any other land." -- Mark Twain