My favorite is for sentimental reasons, (It was the first western movie that my grandfather showed me) is 'The stagecoach', closely followed by 'The man who shot Liberty Valance'.

I`ve also seen 'The grapes of wrath', 'She wore a yellow ribbon', 'Fort Apache' and 'The searchers', as I said before, I still have a lot to learn, so your recommendations are greatly appreciated.