Chalk One Up for God
A certain atheist professor of philosophy had as a primary goal to prove to his students God couldn't exist. At the end of every semester he would say to his class, "Anyone who believes in God is a fool. If God existed, He could stop this piece of chalk from hitting the ground and breaking. Such a simple task to prove that He is God, and yet he can't do it." Then he would drop the chalk and it would shatter into a hundred pieces on the tile floor of the classroom.
If you confront anyone who tries this silly trick, here's how to respond.
Tell the students that you will prove how futile this professor's test is. Have someone stand right in front of you with a piece of chalk and declare that if you really existed in front of them, you could catch the chalk and keep it from hitting the ground and breaking. Then have them drop the chalk and allow it to fall the ground and shatter.
Then say, "I guess this proves I don't exist and that anyone who believes otherwise is a fool. Is this a good test for the existence of God? Of course not. The only thing this professor's exercise proves is that if God does exist, He's not a circus animal that can be teased into jumping through hoops to appease the whim of foolish men.