A couple of years ago, a band named Bon Jovi put out an album called Crush that was intended merely to promote some live shows overseas and pay off a few mullet-replacement-surgery bills. Instead, the recording became their first American hit in years, thanks to the single co-written by Swedish popmeister Max Martin, "It's My Life." Naturally, their fellow Eighties hair-bangers sat up and took notice. So X is Def Leppard's own version of Crush, complete with a Martin power ballad: a big fat Swedish meatball called "Unbelievable." But since the Lepsters always had catchier beats and craftier tunes than the metal competition, they adapt to global pop with their signature sound intact, and X may be their niftiest since Adrenalize. You've heard it before: "Four Letter Word" and "Everyday" shamelessly rip "Photograph," "Torn to Shreds" revamps "Hysteria," and "You're So Beautiful" sounds exactly like "Animal." But what the hell — "Animal" deserved to chart a lot higher than Number Nineteen back in 1987, and it will only be cosmic hair-metal justice if Def Lep score a comeback hit with this one.

“I'm Yours”

Jason Mraz re-emerged after his disappointing second album with this lead single, a Jack Johnson-esque ditty about giving yourself fully to someone else. The success of the reggae-tinged song (it earned two Grammy nods and a spot on the Billboard singles chart for well over a year) was something the folk-pop singer never predicted when he wrote it in 15 minutes at home. "I played a happy-hippie chord progression that would probably work without 50 different Bob Marley songs," he told Rolling Stone. "I thought, 'It's too novelty. This is a nursery rhyme,'" concluding that "you can never guess what's gonna be a hit."