Coen Bro's

One of my favorite scenes of any movie is the opening scene of No Country, up to where Chigurh leaves the police station. It's extremely effective at establishing Bell as the world-weary, old-time style sheriff and Chigurh as a cold-blooded, lunatic murderer. Bell's voiceover along with the long-shots of classic Western scenery does the former, while Chigurh's strangling of the policeman and the look on his face does the latter very well. I think this has to be the best introduction of characters that I've seen in almost any movie.