Cat and Mouse

Source: traditional? (I learned it from Bernie De Koven's A Playful Path; p.81)

One player is the Cat, one player is the Mouse. Everyone else holds hands and forms a circle around the Mouse, while the Cat remains outside the circle. The Cat is trying to tag the Mouse.

In this game, the players who form the circle have the job of balancing the game; they can choose to let the Cat in, or the Mouse out.

Variants:

Grids

Source: Woodcraft Folk Games Games Games

Instead of a circle, players are arranged in a grid, holding their arms out to form uniform lines/walls. The Cat and the Mouse cannot break through the walls.

Periodically, someone calls "change", at which point the grid players rotate 90 degrees to create a new configuration of walls.