What old movies would you suggest watching, and what is/are your favorite black/white movie(s)?

I’m gaining a greater appreciation for the plots and scripts from the days of the black and white movies. I have a few favorites, including Alfred Hitchcock and other film-noir genres. If you have some favorites of your own you would like to suggest, and, if you feel like it, why you liked the movie please post your comment. Also, I’ll include foreign films (with subtitles) in this question too.