I have an idea. I have just read how to make a very cheap taser out of a dispoable camera. I have built it but its useless as a taser. When the two wires touch however, a very large spark is created. To apply that to this, all you would have to do is create a ignition sequence that after activating the "taser", you push a button that touches a piece of metal to both. You can see how to make the taser here: http://www.i-hacked.com/content/view/181/98/
I was thinking of something like this:

So what you would do is:
1. attach the "taser" to the side of the chamber.
2. Drill vary small hole just big enough for the wires to fit through.
3. Feed wires through and tape the wires to the side of the chamber apart but not to far apart with eletrical tape or perhaps use some sort of heat resistant tape.
4. Seal wire hole with watever you please.
5. Drill hole for ignitor switch.
6 Construct the ignitor switch which could be as easy as a bent nail. It wil not shock you even if your holding the medium by which the 2 wires become connected. I have tested this.
7. Fiinsh up by sealing the switch hole with what you wish.
Presto you have a very intense spark when the taser is activated and the 2 wires are joined by a metal object. Trust me this would work and only requieres a nail, some tape, a disposable camera and some wire which you can take out of an old usb cable. Very cheap and very affective for a very intense spark. This spark is so intense it puts small dents where the metal is touched by the two wires. Build the make-shift taser and test it if you wish. The spark is once again very intense. It is much bigger than a flint.
Let me know if you have any questions and if you try it post up your results.
Post up what you think of the idea. I am about to make it. I will begin construction of my spud gun tomorrow with this idea used.
I have read some more posts in the forum and I have discovered that someone has come up with a similar idea to me. I guess great minds think alike.....