American actress and former model Rachel Nichols (Alias, Resurrecting the Champ) will play G.I. Joe's Master Sergeant Scarlett. Scarlett is a counter-intelligence operative and martial artist, and one of G.I. Joe's leading ladies. It'll be interesting to see Nichols pull off Scarlett's kicks and flips in the movie.
Korean actor Lee Byung-Hun (Capcom's Lost Planet) will play Cobra's ninja master Storm Shadow. Byung-Hun is regarded as a very good actor and has received many awards, but I have no idea if he knows martial arts.