Set up
Have a set of clue cards for shapes to give to the actor(s). This can be a deck of cards, with one shape drawing on a card. If your students can read well enough, you can write the name of a shape on each card.
Another option is to have a collection of shapes in a bucket to blindly reach into.
This can be done in a wide variety of configurations. The whole class can try to guess the shape as one student acts out a shape, the class can break into two halves to compete on who can guess five shapes the fastest, you can split into pairs, or pick your favorite configuration. Have any allowed props readily available.
Play
Students are given shapes to act out and the other students guess which shape they are acting out. Once the actor has a shape, the person must act out the shape without making any sounds and without using their fingers. For example, if the shape is a triangle, the actor must make a triangle with some part of their body without making use of their fingers in any way to signal that it has three sides.
Goal
To guess the shapes as quickly as possible
Math Concepts
Properties of shapes
Materials
Set of clue cards and maybe props
Players
Use small groups all the way up to the whole class