What are fun games to play with a 9 month old?

I learned that babies at this age have an appreciation for cause and effect. Meaning if you move the light switch, it turns on. When you move it back, it turns off. They then have this initial feeling on being able to control things. A jack in a box toy can give the baby a thrilling experience of surprise when he opens the box. Read more about this and other games here: http://www.babycenter.com/0_20-fun-silly-development-boosting-games-to-play-with-your-ba_1479310.bc