Gorillaz recently took part in Radio One's infamous Live Lounge, performing 3 delicate versions of their own material and others; its worth checking out all of them, but the stand out track has to be the cover of Crystalised. Only somebody with the musical intelligence of Albarn could pull off a cover of The XX so beautifully; replacing the guitar with piano and adding a xylophone transforms the song into something eerily haunting. I personally can't stop listening to it.
gorillaz - crystalised (the xx cover) by arrhythmiamusic2
Thanks go to SKOA for the uploaded videos.
Don't forget to take a look at Melancholy Hill and Doncamatic too.