6 (tie). Patti LaBelle
Legendary singer/songwriter Patti LaBelle has graced us with her powerhouse voice 21 times since her first appearance in 1991. One of Patti's most moving Oprah Show moments was when she paid tribute to Luther Vandross after he passed away in 2005.
Patti gave us another memorable performance in 2008 when she surprised an unsuspecting fan. Win, a man who described himself as "the biggest Patti LaBelle fan ever," thought he was serenading his wife, Vickie, for Valentine's Day, but he never expected his music idol to join in!