Winchester '73 (1950)

This was the first of the eight films in which Anthony Mann directed James Stewart and it remains one of the best, both for its clever story and for its wonderful cast, down to the smallest parts.  In short, Stewart wins the "one in a thousand" rifle in a Dodge City shooting contest, but it is stolen by the defeated Stephen McNally.  The latter is forced to sell it to gun trader John McIntire who is then murdered by an Indian warrior who covets it (Rock Hudson in one of his earliest roles).  When the Indians attack a cavalry division which includes a very young soldier played by Tony Curtis, Hudson is killed and the sergeant gives the rifle to Shelley Winter's boyfriend.  He in turn is murdered for the rifle by psycho Dan Duryea who eventually returns it to McNally -- just in time for Stewart to kill the latter.  One knows that there is something brewing between these two characters, but the facts are held back until the end reel.  This is the film that started Stewart on his Western mode and it stands as an excellent introduction to this new persona in his career, basically upright but often troubled.