Kickball
Dodgeball
Foursquare
Monkeybars
Tag

Taken from the Portland Mercury News

The goal of the game is to keep the ball moving by hitting or slapping the ball, and for it to land within the boundary of an opponent's square. When you are unable to hit the ball into a square, you are out and everyone shifts clockwise for a new person to enter the game. For this reason four-square is best played with five or more people.

Some fun variations on the game:

Old School Rules:

• Tea Party: Bounce the ball back and forth between one other person and server.
• Fairbacks: Playing gentle and nice.
• Around the World: Bouncing the ball clockwise around the court.
• Bubbles: Allows you to legally "carry" the ball by bouncing it in the air with your fingertips.
• Cherry Bomb: Forcefully slamming the ball into an opponent's square with both hands.

New School Rules:

• Old Crusty Sea Pirate: Jump on one foot and have one hand over your eye while you play.
• Pow Wow: Dance while playing.
• Twice-as-Nice: Allow the ball to bounce twice BEFORE hitting it back. (Also try thrice-as-nice!)
• Pele: Use only your legs, feet and head.
• Jump and Grunt: You must grunt and have your feet in the air while hitting the ball.