This game hardly even needs rules—the equipment is so irresistible, kids immediately devise their own variations.
For each child, have ready a special hat you make ahead of time plus a small, soft object, such as a beanbag or Koosh ball. To make each hat, simply glue two plastic, cereal-size bowls bottom to bottom and fashion a chin strap by either stapling on an elastic band or looping one through tiny holes.
For one game, put kids in pairs about four feet apart. At the whistle, the first player to toss the soft object into his partner's hat, wins.
For another variation, kids are on their own. The first child to toss the object into her own hat wins.