John Denver Mother Nature's Son
Mother Nature's Son has been covered by at least six other artists that I'm aware of, but I always imagine John Denver hearing it for the first time and thinking, "Dang! I should have written that song!"
Paul wrote Mother Nature's Son in response to a particular lecture by the Maharisi Yogi while The Beatles were in India. Lennon wrote the unreleased Child Of Nature following the same lecture (you may recognize the melody, which he reused on the Imagine album).
This has always been one of my favorite songs, and in spite of all of the covers, I think McCartney's version is the best version by far.