You know those little Chinese white paper cracking snapper tadpole looking things you throw at peoples feet to scare them? Here's the really scary version. It's basically the same thing/design, but much bigger--best of all you can launch it long distances with a slingshot.

Step 1: Let's Make It...

Materials:
-Aluminum foil
-Box of snappers
-Small roll of firecrackers/ or anything with gunpowder
-Jumbo marble, or metal ball about the same size--heavier is better
-Slingshot (optional, but recommended for more fun)

1. Cut aluminum foil into 6-inch squares (2 per projectile). Spread out the 2 layers flat
2. Empty maybe 12 or so snappers (little flint rocks and gunpowder) into center of the foil. Spread them around maybe an inch.
3. Unroll firecrackers (maybe 5) to empty out gunpowder, or from whatever source you have available. A nice little pile will do. Start small and work your way up.

NOW IS THE TIME TO START BEING MORE CAREFUL WITH IT. THE FLINT ROCKS WILL SPARK IF CRUNCHED OR RUBBED HARD TOGETHER.

4. Place the marble or metal ball on the pile
5. Pull the corners of the foil up and around, encapsulating the marble and gunpowder mixture, and twist up into a tail. It should wrap up nice and tight for a good explosion.
6. Now either throw it (far) or gingerly put it in your slingshot and launch it. A good tail helps stabilize it. Remember, it needs to hit something hard, like concrete.

Anyway, that's the basic idea--the way we did it when we were kids. BE CAREFUL!

An afterthought: wrap a chopstick into the tail to add stability and make sure the business end hits the ground.