ZanyDoodle is a puzzle game - a very interesting one, from a UI research and development perspective. To solve puzzles, players must 'program' the environment with different (virtual) crayons that represent yarn, rigid bodies, static bodies, and other elements. The images draw are automatically animated by the environment when the developer lifts the crayon.

See a sample video on youtube: 
 http://www.youtube.com/watch?v=WyuIs_JYO6c