Hrmm... there are a bunch. Although with some, I may have prefered them with other bands or previous groups, I still love all of these very much as a solo artist.
Ronnie James Dio (formerly Elf, Rainbow, Black Sabbath)
Ozzy Osbourne (formerly Black Sabbath)
George Lynch (formerly Dokken, Lynch Mob)
Rob Halford (formerly Judas Priest)
Ace Frehley (formerly KISS)
Eric Clapton (formerly Yardbirds, Cream, Derek+Dominos, Delany+Bonnie, and more)
Paul McCartney (formerly some bug-based band)
Yngwie Malmsteen (formerly Steeler, Alcatrazz)
Steve Vai (formerly Alcatrazz, Frank Zappa, Whitesnake, David Lee Roth, P.I.L.)
Those are the first I can think of off the top of my head.