This easy and unike contraption will enable you to shoot marshmellows (or rocks!) at your freinds! (Don't use rocks that was just a joke!)
7 Popsicle sticks,rubber bands,spoon
Put 5 popcicle sticks on top of each other and connect them with 2 rubber bands
Get two popcicle sticks on top of each other and only connect it on one end with a rubber band and stick it to the bar
Secure it in the middle.
Connect the spoon to the contraption you made and put a marshmellow on the spoon pull back and launch!