If you think that Diana Rigg's Regan is bone-chilling, try Asaji, the Lady Macbeth analogue in Kurosawa's Throne of Blood. Her slow departure into the darkness and her return with the drugged wine to give the soldiers is thrilling ("thrilling" in its older, more spine-tingling sense).
The dagger speech itself is also astonishing. Actually, "speech" is something of a misnomer. The sense of the speech is completely internalized! Washizu (the Macbeth analogue) has to express it all without saying a word. Watch:
And the entire film is as brilliant—as stunning—as flabbergasting as that scene. If, somehow, you've missed it, watch the rest at once. At once!
Links: The Film at IMDB.