Simple, easy way for students to brainstorm what they already know about the names of polygons before teaching. I have students spend 2 minutes naming as many as they can and draw. Then, have them pair with a partner to fill in any their partner had that they didn't. I wander the room and give a prize to one or two people who had the most. I display an answer key and lead into discussions about circles being defined as polygons with infinite sides and convex vs. concave polygons. (They soon realize it was easier to draw the concave ones when the number of sides increased:))

Thanks and enjoy!