Make a Simple Projectile Launcher

This simple idea produces an effective "weapon" which could be easily concealed for shooting at a target.

Steps

Start off by collecting the necessary supplies listed below. They are widely available in local stores if you do not own them already.
- Water Bottle
- A knife that is sharp enough to cut the plastic on a water bottle.
- Rubber kitchen gloves used for doing dishes.
- Any ordinary rubber band.
- A file (optional)
Remove the cap of the water bottle and cut off the top a little over an inch below the thread for the cap.
Cut off the widest and fattest finger you can find on the rubber kitchen gloves at the lowest point without cutting into the palm but be sure not to dispose of the rest of the gloves.
Stretch your finger over the bottom of the recently cut piece of the plastic bottle being sure to not cover the spiral part.
Take your rubber band and continue wrapping it around the bottle piece securing the rubber glove finger in place. This is essential to preventing the finger from falling off when firing. This completes the launcher.
To fire, just place your ammo into the glove, hold the "weapon" with a firm grip on the rubber band with one hand and pinch your ammo through the rubber glove while pulling back.
Let go and watch it fly!

Dry Lima beans are great for ammo because although they might not be as accurate as an Airsoft BB or something similar, they are cheap, easy to find in local stores, come in large quantities, are biodegradable and, best of all, they shatter when they hit a semi-hard object.
Chances are, you will still have rough edges which will, after many fires, start tearing and may rip your finger. Thus, save your "unused" fingers to use as replacements.
After initially cutting off the top of the bottle, use a wood file to sand off any sharp edges or burrs left behind from the cut.