All judges of all four shows over the years, in their US and UK incarnations. Vote on your favorites.
http://www.ranker.com/list/judge-the-judges-got-talent-idol-x-factor-and-the-voice/triviafan,
Adam Levine
Blake Shelton
Heidi Klum
Howard Stern
Howie Mandel
Randy Jackson
Shakira
Simon Cowell
Tom Jones
Usher