His cover of the Nine Inch Nails song, "Hurt", is way, waaaaaaay more powerful and moving than the original. Considering that it's an old man singing rather than a young guy who still has his life ahead of him, that's probably why. Made the original writer change his mind on the song's theme.
Of course the original Nine Inch Nails version can be quite the Tear Jerker itself. Johnny Cash takes it, gives it minimalism and dignity, and makes it his own.
Perhaps the biggest respect offered is that when Trent Reznor finally heard Johnny Cash's version of "Hurt", he claimed that "the song is no longer mine." In the world of music, claiming a creation of yours is no longer yours is a degree of respect that you just don't see very often.
Reznor openly admits to shedding tears when he watched the music video for the first time.
For bonus tears, notice this little thing: in the music video, he's still wearing black.note Ref. to his song "Man In Black"
And that his beloved wife had just passed on.
Actually, she was still alive, as you see her in the present day parts of the video. However, the camera cuts to her on the line 'Everyone I know goes away in the end' She died not long after that.
Don't forget Johnny Cash's version of Sting's "I Hung my Head". Much, much better and more poignant than the original.
His cover of Bonnie "Prince" Billy's "I See a Darkness" is heartbreaking.
Add "Love's Been Good to Me" (especially the video) and "Give My Love to Rose." Knowing both were recorded after June died makes them even sadder.
His cover of Hank Williams' "On The Evening Train" for the same reason.
Also, "If You Could Read My Mind" can leave one with a pouty lip and Puppy-Dog Eyes.
"Far Side Banks Of Jordan":
"I'll be waiting on the far-side banks of Jordan I'll be sitting, drawing pictures in the sand..."
Then there is "Don't Take Your Guns to Town".
"Give My Love to Rose" and "Old Shep" Guaranteed to put tears in your eyes.
"We'll Meet Again" for the title alone. The whole song is very touching now.
His cover of "Desperado". Oh God, so much more poignant than the Eagles original:
"Desperado, oh, you ain't getting no younger Your pain and your hunger, they're driving you home And freedom! Oh, freedom! Well, that's just some people talking... Your prison is walking... Through this world all alone."
"In My Life".
The next-to-last verse of "The Legend of John Henry's Hammer" where John gives his hammer to his wife.
His cover of "Streets of Laredo". It's a song about the narrator meeting a dying young cowboy.
"September When it Comes" was written by Johnny's daughter, Roseanne. They recorded this song together six months before Johnny passed away in September...
His death makes "The Man in Black" more than a little bittersweet when you hear the last lines "I'll carry off a little darkness on my back. 'Til things are brighter, I'm the man in black." and know that he never took it off before he died.