7. Black Sabbath
The original line-up of Black Sabbath reunited in 1997 and toured off and on until 2005, but they never managed to cut a new album. The group got inducted into the Rock and Roll Hall of Fame in 2006, and soon afterwards the group reunited with second singer Ronnie James Dio and wound up in a lawsuit with Ozzy Osbourne over the band's trademark. A reunion seemed unlikely, but last year they put aside their differences to begin work on their first album since 1978's Never Say Die!. A world tour is slated to begin in May, but Tony Iommi just announced that he's undergoing treatment for lymphoma. The diagnosis reportedly caused them to back out of a planned performance at Coachella in April, and it's unknown if the other dates are going to happen. We wish Tony a speedy recovery.