Here's a great, unexpected cover of The Cramps "Human Fly" I heard during The Yeah Yeah Yeahs set at Coachella. It's got the same surf punk feel, but Karen O's incredibly unique voice carries this song into new, unique boundaries.
This is a little older, but I love Otis Redding's cover of The Rolling Stones' "I Can't Get No Satisfaction." It gives this rock n' roll song a little more soul, a little more swing and fun to it.
Here's a really interesting take on Vampire Weekend's "Cape Cod Kwassa Kwassa" done by Hot Chip and Peter Gabriel (who is referenced in the song.) Vampire Weekend's version is charming because it's got their fun, bouncy African-inspired instrumentation and percussion. This version lets go of all of that and replaces it with electronic drums and synths. I'm not too sure how I feel about this song. It's a really interesting take, but it lacks the soul of the original. I'd rather dance to Vampire Weekend's version than kind of lounge or sit to this version. Interesting, but not my favorite.
This is a cover of The Kink's "Nothing in This World Can Stop me Worrying About That Girl" by Feist. I think it lacks a little of the mournful soul of the song, it lacks the woes of a man loving a girl that isn't very good for him. This cover isn't mediocre cause Feist is a woman, but because she doesn't convey Ray Davies' feel of loss. Not a bad cover, but not great either.