History Of Violence was decent...there is one split second scene that MAKES the film...if you've seen it you know what it is.
The Fly was classic, definitely recommended (it is the most 'commercial' of his films)
I just bought Spider and haven't watched it yet.
Existence is good, but a little long winded...when I saw it in the theatre it really messed up my conception of reality... on DVD it doesn't have quite the same effect.