One classic game to illustrate gravity involves repeating Galileo's experiment of dropping various objects and timing how long it takes for them to hit the ground. Another fun game requires building an inclined plane or ramp and rolling balls or toy cars down the plane.
Dropping objects into flour or mud also provides a fun way to explore the effects of gravity on making impact craters. Objects of different sizes can be dropped from various heights and the resulting impact craters can be measured.
Younger students can learn about gravity by playing with a pencil. Simply balancing the pencil over a finger demonstrates the pull of gravity. Various objects can be attached to the end of the pencil to see how they affect its balance point.