I picked up a DVD from Tesco for a £5, the original 1932 Scarface starring Paul Muni, George Raft and Borris Karloff, directed by Howard Hawks. Widely considered to be one of the great Gangster movies and a film that influenced all future gangster movies.
There is a very interesting montage scene that suggests a passage of violent time in the career development of the hoodlum Tony. Pages of a large desk calendar are flicked away like plying cards with a superimposed image of a machine gun firing as the numbers of the month are flicked and fly away.
Hawks also used lighting to create shadows representing the killer in a couple of scenes and in the scene recreating the famous Chicago Valentines Day massacre shadows of the victims to simplify these shots and add extra drama.
I noticed that Hawks used a lot of long takes dollying the camera to follow a character before panning and refocusing on a new character.