Actors pass on roles all the time -- it's part of the movie business. Take Leonardo DiCaprio. His enormous box-office potential makes him one of the most sought-after actors in the world. As such, he's been offered the opportunity to play numerous big-time characters, a few of which he's had to turn down. (Not infamous FBI director J. Edgar Hoover in Clint Eastwood's 'J. Edgar,' which opened this week.) In honor of DiCaprio and his Hollywood brethren, let's take a look back at some of the biggest roles actors have ever turned down.