Quote:
the redemption of youtube through Johnny 
of course the ever popular "Ring of Rire" and "I Walk the Line".
Ring of Fire
I Walk the Line
Not very original choices, I know, but these are also my two favorite Cash songs when it comes to his old stuff. From his American Recordings era I enjoy his renditions of U2's "One" and NIN's "Hurt" the most.
Some Cash trivia
Did you know that Johnny Cash recorded German and Spanish versions of his songs for the European market? -> Article
If you want to listen to "I Walk The Line" in German ("Wer kennt den Weg?", which translates as "Who knows the way?"), then click on this link.