1.
This is a pretty old trick but still very impressive. If you take a wooden ruler and lay it on the edge of a table and try to break it by bringing a force down on it, the ruler will just fly off of the table. But when you lay a piece of paper on top of the ruler then the surface area that the air is resting on is much greater than it was when it was resting on the ruler alone. So with all of the air pressure on the newspaper, the ruler is unable to move when quick force is applied to it, causing the ruler to break. Give this trick a try, but be careful, the ruler can fly up and hit your face or hit an object in the house.
2.
A large wooden paint stick is "karate chopped" in half using air pressure, and some ninja skills.
Tip: Plastic wrap works great and is as easy as it looks. If you try this with a plastic bag, the bag has to be completely smooth and as wrinkle free as possible. If you're having trouble, try wiping down the surface of the table with a damp cloth. The surface needs to be extremely clean, and the water residue will help form a better seal between the table and the bag.