Catapult | Materials: craft sticks, rubber bands, 1 lid (Spoon or lid from milk jug, soda bottle, etc), glue gun or glue, and stuff to throw (cotton balls, scrunched up paper balls, etc) | Instructions: http://littlepaperdog.blogspot.com/2012/11/popsicle-stick-airplane-catapult.html
20+ Creative and Instrutive DIY Catapult Projects for Kids
Pencil Catapult. This catapult is built out of unsharpened pencils, rubber bands, and a plastic spoon. The process of making is so easy, your kids can make it by themselves just according to this picture. http://hative.com/catapult-projects-for-kids/
Catapult using plastic spoon, Popsicle sticks, cork, & rubber band. I added a second rubber band near the end of the spoon handle to secure the spoon better. Ask kids to experiment with the placement of the cork to see if they get more or less distance with projectiles. Let's use marshmallows or pom poms for shooting! This is one of the more frugal stick catapult designs I found, using only 2 sticks. Also, there is no gluing, so no wait time betweening making and playing.
catapult design by a 7th grade student. 12 Popsicle sticks, a rubber band, a plastic spoon and some hot glue. Assignment: design a catapult capable of lobbing mini marshmallows into your neighbor's castle. Mini marshmallows are ideal for a mock medieval siege because they are 100% safe of they hit you.