I made it out of a few household objects, it launches Q-tips anywhere between 30-50ft.

Step 1: Supplies

1.Pen (all you will need from it is the plastic body for the barrel, so make sure you can fit a Q-tip inside of it)
2.Pill Bottle (the small kind that are like an inch in diameter)
3.Electrical or Duct tape
4. PVC Glue or some other type of glue that is very strong (i only used pvc glue becuase i found some in my garage)
5.A sparker- There are two possible sparkers you could use
1. I took a grill lighter and took it apart and just took out the butane tank and the long metal neck thing, so when it was done all i had was the body of the lighter with 2 wires sticking out of it ( there a picture of it on one of the next pages). - You will need 2 screws for this type of sparker
you can also use a grill sparker which would be easier
2. The other type of sparker you could use is a lantern sparker, i haven't actaully used one of these on something this small but i would guess it would work.
6.Drill with small bits ( obviously for putting the small holes in the pill bottle)

Step 2: Assembly

This really is pretty simple,
Step 1: Take the pill bottle and drill a whole in the bottom of it, the hole should be the same diameter as the pen or maybe a tiny bit smaller. You want to keep the hole small so that when the barrel goes into it theres not a lot of apace around it.

Step 2: Take your pen apart, all you need from it is the plastic tube body. Take the tube and fit it into the hole that you drilled into the pill bottle, and then slap some of the PVC Glue on that, make sure you seal up all the cracks, otherwise the gun will not work.

Step 3: If your using the grill lighter as a sparker: drill two very small pilot holes for the screws to go into. Then screw the screws into the hole leaving them stick out a little bit, you want the tips of the screws about 1/8 inch apart, if they're too far apart or if they're touching , it won't spark.

Step 4:Then take your wires from the sparker and attach them to the screws, and test to see if it sparks if it doesn't adjust the screws until it works then take the wires off the screws and PVC glues the screws in place, this also seals the bottle better, and then reattach the wires to the screws.

:Edit:
Step 5: I finally made one with an lanter sparker in it, it took awhile but it works quite well. The only problem is that i can't get hair spray work with the sparker, but i found a solution. Gasoline, simply dip the end of a Q-tip into some gas so it soakes it in, then swab the bottle in one complete circle around the inside with the gasoline soaked Q-tip, then close the cap put the Q-tip in the barrel and fire.

Step 3: Firing

To fire, put a Q-tip in the barrel, make it doesn't slide down into the bottle part just spray a very small amount of hairspray into the chamber and very quickly close the top, if you do this part to slow the gases will escape and it won't fire, if you use to much most likely it won't fire due to not enough oxygen, or if it does the bottle could possible explode.

If you want you can wrap the bottle part in electrical tape, if you put duct tape on the screws the electricity from the sparker will go through it, so use electrical tape.

In the video below I used a lantern sparker, and I used propane from an old lighter which I stuck a small piece of tubing on the end of, its actaully just the outside casing of copper wire.