This is a free cardboard version of a $50 crossbow, made from junk, designed to fire drinking straws. I designed and made this model myself, with my kids and we had great fun with it. You'll need a rubber band, a couple of wire coat hangers, a wine bottle cork, a couple of old ball point pen barrels and some corrugated cardboard. Free templates for the wood pattern can be found at dadcando, where there are a few other projects that you might be interested in.
Step 1: The Shape of the Crossbow
Download the template from Make a crossbow
Step 2: Cut Out Card and Stick Together
Using the templates, cut out the card and stick together, making sure to put the cork in with the trigger when you are half way though sticking the layers together.
Step 3: Use Wood Effect Paper Inkjet Printout
Use wood effect paper inkjet printout to make the crossbow look realistic. Sorry these instructions seem so lame, I made a printout of the full instructions with templates and wood effect area which you can get from Make a Crossbow as a pdf. However, you can also enlarge them up from these images here on Instructables and print them out from your web browser window. Enjoy...