Rihanna rarely sings alone. She's almost always accompanied by another singer, drowned out by synthesizers or Auto-Tuned by an overzealous producer. But tonight, at least briefly, it's just Rihanna and the microphone. Then Eminem appears and does the unthinkable: he makes the performance even better. When the duo performed "Love the Way You Lie" at the MTV Video Music Awards earlier this year, they seemed disjointed and unrehearsed. Here, they've have found their element. And Dr. Dre, whose cameo could have been an unnecessary addition, only added to the fire.