In ancient times, catapults were instruments of war. Our modern version comes in peace, offering its operator the fun of hurling marshmallows into a friend's mouth.
Expand the opening of the tissue box by cutting off the sections shown.
Punch a hole 2 inches from one end and 1/2 inch down from the opening of the box. Enlarge the hole with the ballpoint pen. Make a matching hole on the opposite side of the box.
In the center of the far end of the box, poke a hole with the pushpin 1/4 inch up from the bottom. Enlarge the hole slightly with the ballpoint pen.
Snip one rubber band to create a strip. Use the strip to wrap and tie the pencils into a cross, as shown. Loop the other band around the 2-inch pencil section as shown, and tighten.
Insert the pencil cross into the box holes. Fold the pipe cleaner around the rubber band loop and poke both ends through the hole near the base. Spread open the pipe cleaner ends and tape them to the outside of the box. Attach a plastic cap to the end of the pencil with a couple of glue dots.
To use your catapult, pull the capped pencil back, load it with a marshmallow, and let go! (To be safe, do not launch any hard or sharp items.)