"1 Thing", by Amerie.
You can watch an official-seeming video here. Sorry it looks a bit too "Video Hits", but you can just shut your eyes and listen.
I have written about this song before. It remains one of my favourite pop songs of recent years. It appears, in a curious context, in Sofia Coppola's new film, "Somewhere". Probably the easiest decision Sofia Coppola could have made, given her unchosen status as daughter of Hollywood royalty, would have been to have nothing whatsoever to do with the making of movies. That she did not make that decision, and has given us, now, four feature films, at least three of which (I'm not sure yet about "Marie Antoinette") are nothing short of wonderful, is a modern miracle.