This is a catapult built into an altoid can. It uses pretty common items:
1x Altoid can
2x Clothes Pins (ones with springs)
2x Rubber Bands (Preferably small ones)
1x Assorted piece of flat wood.
Hot Glue Gun
Small Metal Saw
First thing you should know is that not everyone of these things turns out perfect, or even useable. If you dont think any of the things I used to make this is perfect, do not be afraid to change it. The one that i made during this instructable turned out to be a flop, because i tried some new methods, compared to the last one. Ill try to include notes to help you make a beautiful catapult.
Step 1: Prepare Fulcrum
Toothpicks, or whatever round piece of wood you used (i used a "bamboo skewer", which turned out to suck) Try to use something as thin as possible
First, Remove the metal spring things from the wood of the pins, and strech them out a little, so the legs are about 1/2 an inch apart when they stand up.
Next, cut a piece of the toothpick that is just a little longer than the width of the can. Now, shave the toothpick down so that it fits smoothly into the hole of the springs. Shave it down with whatever you feel like.. scissors, file, teeth... and make sure to clean up the mess.