Speaking of Gnarls Barkley, soul singer Bettye Lavette takes their hit "Crazy" to new places by stripping down its production to a slinky nightclub number and really wrenching the vocal phrasing as wide open as she can. The result is quite fantastic. It goes from being a piece of unstoppable momentum, to one where you just hang on every word.
The last few years have seen Lavette on a tear, making up for lost time (look her up on Wikipedia.) One of the best examples of her power is what she does to "All My Love," probably the most-maligned song in the Led Zeppelin songbook. By transforming the tense synth they used on their recording with a much broader piano stroke, she lets the emotion pour into it, and while the song doesn't sound as mournful as it was originally recorded, it also doesn't sound as cold and cut off. Staggering.