Invasion U.S.A., and more recently the Marlon Brando picture On The Waterfront. After a little bit of research I found that both of those posters were done by Italian artist Anselmo Ballester. His signature is visible on both of them, I just didn't know who it belonged to. According to his ItalianWiki page, Ballester was born in Rome in the late 19th Century and did art for political posters before he did movies.
Above is another one by Ballester, for the 1947 film T-Men, directed by Anthony Mann, but I also highly reccomend this awesome gallery of Ballester's work. The site is in Italian, but the images are clickable and of course, beautiful.