Seeing as there is a worst cover version ever topic one to counter it for me its either:

Metallica - whiskey in the jar or Trivium - Master of puppets

i love smashing pumpkins doing thin lizzys dancing in the moonlight

Don't know about best ever, but I really like the Barenaked Ladies version of 'Lovers in a Dangerous Time'. Beautiful song.

Somewhere over the rainbow by Eva Cassidy.

Or as somebody said before, hurt by Johnny Cash.

I'm not really a fan of his. I just like a couple of songs

The Cardigans - Sabbath Bloody Sabbath

Dead Kennedys - Viva Los Vegas and I Fought the Law

That song should only be sang by the Undertones...

It can't be better than the original!

I should listen to it before I say all of this.

A great cover..

Blister in the sun - Janes Addiction.

Alizee - La Isla Bonita http://video.google.com/videoplay?docid=3163993089676547044

Karen Parry - FlashDance

wooo yh marilyn manson tainted love!!!!!!
and whoever mentioned me first and the gimme gimmes you have excellent taste i totally agree
then theres goldfinger- 99 red baloons
sublime- come on eileen
oh der how did i forget sid viscious my way it rocks and limp bizkit faith
lol i could go on forever with punk covers they are all brill

My Way - Sid Vicious