What's your favourite black and white movie?

Old movies kick ass. Many are absolute classics, and I don’t know about you guys, but when I watch a black and white movie, it’s a bit different than a colour one. It’s just not the same as watching colour, and to me it invites my imagination, and many times, offers a great atmosphere.
Actually, my friend says I feel that way because, obviously, most black and white movies come from a generation with cultures that I’m not familiar with, (not to mention that the methods for making movies has changed a lot, not sure what she means though) and it actually has nothing to do with the fact that it isn’t in colour. (as opposed to colour movies set in a period I wasn’t living in, but made in the recent times) Still, whatever, I can’t decide between Nosferatu or Night of the Living Dead. What about you?