Before the New York Times pay wall goes up on March 28th, check out this quirky little game they have on their website. Basically, you're playing Rock-Paper-Scissors against a computer, and as you play the AI tries to statistically "learn" your patterns. So theoretically, the more you play, the worse you'll do...right?
The NY Times offers two levels, Novice and Veteran. In Novice, the computer will only learn from your actions. In Veteran, it uses the knowledge of all players against you.
Check it out and see for yourself. I played several games and it totally kicked my butt.