Gravball
From Halopedia, the Halo wiki
Gravball[1] is a popular game played by Human children. The game consists of a floating gravity ball, and it is played on repulsor courts. The gravball is "skimmed" across the court.
It is a popular activity avaliable on playgrounds. As a child on Eridanus II, John-117 enjoyed gravball so much that they stopped letting him play it because he always won.
NOTE: The mechanics of the game have never been mentioned.
