Let's get started...
Timothy Olyphant as John Marston
John Marston is a retired outlaw who joins a marshall's service to help hunt down his old gang. Olyphant is a great actor. I mostly chose him for this role because of his acting on the tv show Justified.
Rebecca Hall as Abigail Marston
Abigail Marston is the wife of John Marston, and the mother of Jack Marston. Hall was brilliant in The town, so I think she could nail the role.
Logan Lerman as Jack Marston
Jack is the son of John and Abigail. Logan is a great young actor, and he looks a lot like Jack.
Richard Dreyfus as Edgar Ross
Ross is the main investigator hunting down John's old gang. Dreyfus is a great actor, and looks a little like Ross.
Nicholas Cage as Archer Fordham
Fordham is Ross's partner on the case. I really didn't know who could play Archer so thats why I picked Cage.
Sam Elliot as Landon Ricketts
Ricketts is a retired gunslinger turned lawman. Elliot is a veteran actor who is very well known to western's, and he look's the part.
Naomi Watts as Bonnie Macfarlane
Bonnie is responsible for saving John's life after he was shot. Naomi is beautiful, and she would fit the role very well.
Daniel Day Lewis as Dutch
Dutch is the leader of the gang that John was recently in. Lewis is great as a villain. I picked him mostly because of his role in Gangs of New York.
Bill Murray as Nigel West Dickens
Dickens is a con artist who helps John in many of his actions. Murray is very good at playing different role, so I think he would be quit brilliant as Dickens.
Steve Buscemi as Seth Briars
Seth is a deranged man who is on the search of hidden treasure throughout the game. Buscemi is very well strange and thats why I picked him for Seth.
Jeff Bridges as Bill Williamson
Bill is the one responsible for shooting John, and he was one of the members in John's gang. Bridges was great in True Grit,so I think this role would suit him well.
Gene Hackman as Uncle
Uncle is well John's uncle. Hackman is a great actor, so I think he would totally be able to nail Uncle's role.
Sam Rockwell as Harold MacDougal
Harold is a studying doctor who helps Marston later in the game. Rockwell is a great actor and looks the part.
Thats my cast. Tell me what you think in the comments.