9. Edward Norton in Leaves of Grass (2010)
It might seem rather easy to play twins in a movie when they are so outwardly different (Bill Kincaid is a smartly-coiffed Ivy League university professor and Brady Kincaid is a long-haired drug dealer), but Edward Norton is an uber-talented force to be reckoned with. He goes far deeper than the surface differences dictate and provides a great range of familial similarities at the same time. This oft-forgotten little indy gem is prime research material for any actor preparing for a dual role on stage or screen.
8. Half the Cast of Battlestar Galactica (2004)
This is, too put it far too lightly, cheating a bit. In fact, there's nothing "bit" about it. It's flat out Cheating with a capital C. You see, the characters I'm referring to in this epically wonderful reboot of the 1970's classic are not really twins at all, but rather clones of a sort. Still, the actors who are playing the clones-of-a-sort are still required to utilize all the same skills that someone playing true twins has to, including, but not limited to, portraying identical characters with different personalities. For those few who have yet to witness the (almost) perfect series for the first time, I won't get all spoilery and spill the beans on who all the cylons (those rascally clones-of-a-sort) are, but at least one can be mentioned: Tricia Helfer, Number 6. Granted, she wasn't the most experienced member of the cast, but as the series grew so did her talents. Just a quick look at the wonderful differences between her Caprica 6, Shelly Godfrey, and Gina Inviere proves it.