I have, in my time, played in the Known World, Krynn, the Forgotten Realms, a smattering of Greyhawk, Ravenloft, Golarion, Kalamar, 1920s Cthulhu, the World of Darkness, the Wild West, Middle Earth, Smurf Village, Kaidan, the Realm of Dreams, New York with the Ghostbusters, a variety of homebrew...