Security through kittens
From Schneier's blog:

You've all seen CAPTCHAs. Those are those distorted pictures of letters and numbers you sometimes see on web forms. The idea is that it's hard for computers to identify the characters, but easy for people to do. The goal of CAPTCHAs is to authenticate that there's a person sitting in front of the computer.

KittenAuth works with images. The system shows you nine pictures of cute little animals, and the person authenticates himself by clicking on the three kittens. A computer clicking at random has only a 1 in 84 chance of guessing correctly.