Kat DeLuna

Kat DeLuna's always been a half-step behind Rihanna, but on her latest single, DeLuna leapfrogs over the singer, borrowing that fabulous updo while turning Rihanna's rock flirtation into a full-blown affair. "Unstoppable" has the sassy chorus of a guaranteed pop hit and the kind of sandpaper guitar that will grind you into submission, courtesy of none other than Lil Wayne. Yes, our little R&B crooner is all grown up, and -- in a kind of robotic, overproduced way -- fierce! Featured on the Confessions of a Shopaholic soundtrack.