This is an Instructable on how to make a small slingshot-like thing

Step 1: Things You Need

Bottle, Box Cutter, Balloon, Lighter, Scissors.

Step 2: Cutting the Top

Use the box cutter to start the hole, then take the scissors to cut the rest, again using the scissors make sure you just have the circle, then take the lighter and melt it a little bit so the edges are not sharp.

Step 3: Cutting the Balloon

Cut the balloon into thirds, take the big one and pull it over the threads and take the second biggest third and wrap it around the threads to keep the big one on.