...and better than the original.
Jonathan Coulton, Baby Got Back (original)
Obadiah Parker, Hey Ya (original)
Travis, Hit Me Baby One More Time (original)
Michael Hedges, Come Together (original)
Humble Pie, For Your Love (original)
Not a cover: Fiona Apple giving one of the most compelling performances I've ever seen.
Also, the only reason that Johnny Cash's version of Hurt isn't on the above list is because you've already seen it. Right?