I've been a fan of film noir over the years, The Maltese Falcon being my favorite example. But The Killers (1946) has a great intro that I've posted below. The way these two thugs riff off of each other is hilarious. That's one of the best things about film noir besides all the great shadowplay; the dialog.
The Killers stars Burt Lancaster in his first film and the beautiful Ava Gardner. If you love this intro you may be disappointed if you rent it to see the rest....the two bantering hitmen are only in the beginning of the film.