We don't have to go too far back for this one.
Every now and then, a song comes around that just grabs you by the throat, and won't let go. It works its way into your brain, and whether you want to or not, you find yourself singing it to yourself, in the shower, walking down the street, or just sitting at your desk.
"I Gotta Feeling," by the Black Eyed Peas, is just that sort of song. The #1 song on this date, 2009.
P.S. I almost feel like I should post a PG-13 rating on this video...