9. Barbra Striesand & Neil Diamond - "You Don't Bring Me Flowers"
One of the greatest duets in history was actually a fluke: Each cut was a take of this Neil Diamond song individually. But in 1978, a scorned, just-divorced radio jockey from Louisville, Kentucky, spliced them together as a spiteful missive to his ex-wife. Thus an apparently messy end sparked a beautiful beginning: The makeshift duet was so popular that Diamond and Streisand were compelled by their label to record an actual duet, which brought the pain of a break-up to a whole new level — and shot to Number One on the Billboard charts.