I'll admit that while I knew of John Prine, I was mostly ignorant of his music. But I did know the he was a songwriter's songwriter (cf. Roky Erickson, Daniel Johnston, and Leonard Cohen), and was revered by people I revere, such as Bruce Springsteen and Bob Dylan.
I'm marking his passing with one his most celebrated songs: "Sam Stone", from his 1971 debut LP. Today I learned that this song was referenced via melody in Pink Floyd's "The Post War Dream" and lyrically in Spiritualized's "Cop Shoot Cop", which are both on extraordinary LPs: "The Final Cut" and "Ladies and Gentlemen We Are Floating in Space", respectively.
John Prine - "Sam Stone" -- live 1997, Sessions at West 54th; live 1988, Austin City Limits; 1971 LP Version
Bonus link: Johnny Cash, "Sam Stone" -- live 1987, Austin City Limits