The most memorable cover I've heard in a long while
http://www.youtube.com/watch?v=UGDLT-AUQCII need a poultice of Brylcreem & gear lube to get the little hairs on my neck to lay down again
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Always a wealth of covers from the Bluegrass folks
http://www.youtube.com/watch?v=ApQHQPSUErc----------------------------------------------
This one is in my opinion, a modern masterpiece of covers,
although there isn't much post-Dinosaur stuff that Don Was does that I don't enjoy
http://www.amazon.com/Rhythm-Country-Blues-Various-Artists/dp/B000002OR2Scroll down to audio samples near the bottom for a listen.
Reba McEntire's voice on this recording could tear a hole in the soul of the devil himself &
"Patches" sung by George Jones & BB King?... Phew!

I used to play this cover of "Patches" turned up to 11 to get the kids outta bed for school.
They hated it -- I loved it. It's all good. Bet they still remember the lyrics.
(Gotta give 'em some culture you know)
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Koko Taylor does Ted Nugent's "Hey Baby" like it was written just for her. Can't find a link though.
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Here's one for fun from the distant past, recorded on "The Johnny Cash" TV show
http://www.youtube.com/watch?v=8Ydy_EakGfY