Red Hot Chili Peppers, Gnarls Barkley

Unless you spent 2006 under a rock—without the aid of an iPod, cell phone or BlackBerry—these two acts need no introduction. The "Go, go Gadget" success of Gnarls Barkley's St. Elsewhere, the first collaboration between Goodie Mob's Cee-lo and renowned producer and mash-up artist Dangermouse, provided the perfect summer soundtrack as everyone from Cat Power and Paulo Nutini to your mom were caught singing the infectious lead single "Crazy." Judging from the group's smoking hot ACL Music Festival performance earlier this year, expect outlandish costumes and some choice covers by artists such as the Doors and the Greenhornes. Meanwhile, Red Hot Chili Peppers officially entered into the realm of dinosaur rock with their excessive double album, Stadium Arcadium, which successfully rewrote "Under the Bridge" for the zillionth time. Regardless, Anthony Kiedis and Co. remain as popular as ever while their live performances have only strengthened with time, though the band will likely leave their trademark tube socks at home. Prepare to get Freaky Styleyand avoid any songs that even mention California.