Quite often, film casting decisions are no-brainers; universally praised before the cameras even begin rolling. Jack Nicholson in One Flew Over the Cuckoo’s Nest and Batman. Meryl Streep in anything requiring drama and an accent. John Wayne in, well, every John Wayne movie (that is, except playing Genghis Khan in The Conqueror--what were they thinking?). But sometimes, the powers that be like to take chances. Big, crazy chances. More often than not, they end disastrously (et tu, Vince Vaughn in Psycho?). But once in a blue moon, a little bit of cinematic magic happens. Here are 8 great examples.