I've recently built this little crossbow out of more things laying around at home. It's a smaller, and less powerful version of my other pocket crossbows posted here: http://www.instructables.com/id/Tension-pocket-crossbow-No-rubber-bands-or-cloth/
After building and playing with those, I decided I wanted something that could fire toothpicks. Not something that smashed my toothpicks to bits as they hit the wall. Something with less power, and something that won't have a high chance of breaking in my pocket. I've built plenty of Peg guns out of cloths pins, but I wanted a crossbow, and one that didn't use a rubber band as it's source of power. So, with my other crossbows in mind, I made some changes. The bow got smaller, I added some rigs to hold the crossbow together while in my pocket, I created a case, and I made it storeable. When in the case it's slightly larger than a tube of chap stick. But only so I know which one is my chap stick.
I am in NO WAY responsible for what you do if you decide to try and re-create what I have here! Keep it safe, don't point ANY fire arm (in this case crossbow) at ANY living creature! Unless it's a plant, or bug. Bug hunting can be quite fun.
As for the stock, it's made out of popsicle sticks, hot glue, pieces of paper clips, duct tape, and Q-tips.
The bow is made out of a steel blowdart with the sharp tip cut off, jewelers wire, and jewelers crimps.
I modded my bolts to contain steel tips, this added to the accuracy, and power. At far distances the tape on the ends of the bolts can cause the bolts to fail to maintain a straight trajectory. But what do you expect? They're tooth picks.
The case is made out of an old marker, cut into 3 pieces, taped together, and a wire around it to keep it closed.
As far as i've seen, this is the only real toothpick crossbow, and the only real pocket crossbow. All of the other "Pocket Crossbows" I've seen utilize rubber bands, and would crumple to pieces if you put it in your pocket. (I am of course not counting the one created by the jeweler, T. Shamir.) But, I could be wrong. I'm interested to see anything that doesn't use rubber bands and is small. So if you know of one, please post a link.