This game works best for younger students learning the basic shapes of geometry. Using construction paper of different colors, cut out a variety of shapes of different sizes. You can have different kinds of triangles, different sized circles and squares or anything else. Make sure there are two of each figure you cut out. Place all the figures in a shoe box. Cut a hole on each side. Have one student reach his hand in and pull out a shape. He must identify it out loud. Have another student reach into the box on the other side and try to pull out its twin. He must say the shape out loud. Keep going around the class until a student finds the matching shape.
Cut out a number of different construction paper shapes of various sizes and colors. Prepare your classroom by hiding them around the room. Have a treasure hunt, giving students a set amount of time to find as many shapes as they can. You might assign a point value to each kind of shape and write it on the board. If there is a difficult new shape you are trying to teach, have only one or two of those hidden and assign them a high point value. The student to amass the most points wins.
This game can played with the whole class together. Think of a geometrical shape that you have been teaching. Have students raise their hands and ask questions about it. They might ask such things as "Does it have right angles?" or "Does it have more than three sides?" or "Does it have sharp corners?" After a pre-determined number of questions (it can be fewer than 20) have the students guess the shape. Have a student come to the front of the room and think of a shape for the next round.
Take your class outside on a nice day. Have students go around the schoolyard and find one geometric shape that you have been studying. For instance, they might find a rectangle in a window of the school, a circle on a basketball hoop or a triangle in the play structure. Bring students back inside and have them draw the objects that they found. Ask them to use crayons or colored pencils to highlight the geometrical shape in the drawing.