Here's a couple that I've watched recently -
39 Steps. The Robert Donat one, directed by Hitchcock. Piece of Haddock. What causes pip in poultry?Obscure? Not really. But great.
The Mutual Charlie Chaplins. They're very early and a two DVD set has just been released by the BFI. They were much less sentimetal than I expected, with a really nice line in anarchy and just incredible stunts.
Also, I was really blown away by "M" starring Peter Lorre as child-murderer when I saw that a few years ago.