I didn't realize how powerful this thing was till i finished, with that said you should really be careful where you point this thing, and be safe!:) Its really easy to make, and im surprised there wasn't a good tutorial on how to make one of these here. All you need is a metal coat hanger, a strong elastic band, a clothespin(wooden or plastic) and some tape. And if you know what your doing this should only take about 3 minutes of your time.

Step 1: The Frame

So once you have a metal coat hanger you can go ahead and get started. You must bend the metal until the hanger is in a crossbow shape, you can as well bend the hook down so that it turns into a handle. Just look at the picture.

Step 2: Trigger

Your clothespin will be the trigger. It must be secured with tape or elastic bands to the space just below the hook(which is now the handle) with the part that pins down facing outward.

Step 3: Bow String

Place the elastic band stretched out at the two outer corners of the coat hanger so that it looks the same as in the picture

Step 4: Finish and Load

Your pretty well done now, this crossbow shoots pencils,short arrows, and bolts approximately 20-30 ft. Heres how to load it.
To load it with a pencil is quite simple, put the end of the pencil against the one side of the elastic band and push it all the way back into the clothespin. The clothespin will grasp the end of the pencil and the elastic band behind it until you push down on the end of the clothespin and everything is released. It would also be easier to load if you cut a nock in the back of the pencil for the elastic band to sit in. All the supplies for this can be found anywhere in your home so it wont cost much. This was one of my more simple projects so I'm open to any suggestions. Have fun and dont hurt yourself:)