The theory that if you ever see Chow Yun Fat wave his index finger in a movie that he's in, he's doomed. Check it out in "A Better Tomorrow", "The Killer", "The Corruptor", "City on Fire".

However, much like the Spice Theory of Solo Cinematics, the theory doesn't hold much water when you see Chow wave his finger in other movies like "Anna & the King" and "A Better Tomorrow II".