Rihanna: "Diamonds"

Chris Martin took to Twitter to declare Ri-Ri's newest one of his "favourite songs." Not a shock: It's very close to Coldplay soul, a striking turn into lustrous power balladry after a string of filthed-up R&B sexcapades. Written by arty Aussie diva Sia and produced by Benny Blanco and Norwegian hitmaker Stargate, it's glassily curvaceous and strikingly spare: "Find light in the beautiful sea/I choose to be happy," she sings over an ice-flow piano and cascading beat. If she really has started things back up with that other Chris, then this hits the perfect, vaguely creepy note of against-the-odds hope for the occasion.