Clothes pin gun
I am dating myself this toy was popular with my my Boy Scout troop
back in the early 50's. If our parents ever knew about it they never stopped us.
Uses small paper wads, dried peas,wooden match bits, etc. as ammunition. Caution - although this can be considered a toy the ammunition is fired with force and can really sting. Can put your eye out.
Step 1. Assemblying the zapper
Take clothes pin apart and file (or cut) a right angle in the spring groove of one side of the pin as shown. Reassemble the pin using a rubber band as shown.

Step 2. Cocking the zapper
Place the spring on the outside of the zapper as shown. Push on the inside bar of the spring (I used the half of another cclothes pin) until the bar rests in the right angle notch you filed in step one. Place ammunition where indicated

Step 3. Firing the zapper
The barrel of the spring serves as the trigger. Pull the barrel towards the rubber band so that the inside bar of the springs pops out of the right angle notch.The bar will send the ammunition flying. Be careful where you aim the zapper.