Guess the Graph is a 2-player game of deduction. Your students only need to be introduced to the Cartesion Coordinate Plane in order to play this game. Students ask each other yes or no questions in order to determine their opponent's mystery graph.
I love to play this game before our formal instruction with linear graphs. I take note of the questions students ask each other. Such as:
"Does your line go up like this?" while using hand motions, and
"Does your line go from the bottom left to the upper right?"
Once we begin this lesson, I remind them of the questions they asked each other, then give it a name: positive slope.
Playing the game before the lesson allows the students to recognize what the important aspects of the graph are (slope, points, and intercepts) without being told. We are just there to give those aspects names.
I hope you and your students enjoy this game. Look for more editions coming soon (parabola, conic sections, etc).