Here is the instructable that I promised to make if my goal was achieved. It is a bit difficult to make due to the fact that it is round and you are drilling on it and it is simple to use.
Step 1: Part One Materials and Moveing Them to Workplace
Gather your materials and take them to your work place. You will need a toilet paper holder (it does not matter if it is metal like mine or if it is plastic) that comes apart into two pieces with a spring in it, some plastic cutting knives that you use at bbq's and such, a drill (not shown), scissors (not shown), a drill bit big enough for the nail (not shown), a thin nail, and tape (either duct or electrical I used both in my prototype). Optional things to use are a close pin, spray paint, and hot glue. Also in this I did not make another one I just used the one I had so ignore the close pin.
Step 2: Part Two Gearing Down Your Toilet Paper Holder
This should be very simple just pull the big end from the small end and there should be three parts a big end with a spring in it and the small end which will hold the knife.
Step 3: Part Three Prepareing to Drill
Be very carful on this step due to the fact you can lose the small end inside the big end and that you are using a drill. Put the small end inside the big end with the hole facing out as shown in the picture. Put it in so there is only around a few centimeters out of it. I am sorry for using centimeters I am using it because it is less than an inch. Now drill your hole into it.
Step 4: Part Four Preparing the Knife
Now take your plastic knives and cut the ends off as showed in the picture. Then take the blade ends of both of them and overlap them as shown in the second picture. Then tape or hot glue them together and tape the bottom big enough so it stays in the hole of the blade housing (small part of toilet paper holder).
Step 5: Part Five Adding Trigger
Take your nail and put it inside the hole you drilled as shown in the picture. Then tape the end of the nail that is hanging out of spring housing (big part of toilet paper holder) and make as big as desired. If you are using the close pin ignore this step.
Step 6: Part Five (close Pin Trigger)
If you want it to be a one hand use for this drill a hole in the top of the close pin that goes through both sides of it. Then take your nail and make sure it is long enough. If it is too big get a smaller nail or cut it to the desired size. Then hot glue the top of the close pin with the nail head showing so that the nail moves with the close pin. Then hot glue the close pin to the spring housing.
Step 7: Part Six Loading
Depending on how powerful the spring is inside of your toilet paper holder you may be able to do this by hand if not you will need to use something sturdy and still to load it like me. Put the blade housing inside the spring housing quickly and put your nail inside to hold it in place. If you are using the close pin method hold the close pin so that the nail is raised and put the blade housing in the spring housing and put the close pin back so the nail is in place. Then put your blade in the blade housing.
Step 8: Part 7 Fire
Just aim and pull the nail or squeeze the close pin and it will shoot. it will begin to spin after a while and it goes around 15 feet or so. It is also helpful if you paint the blade a bright color just if you lose it due to it falling out upon landing or impact. It does not hurt to be hit with. Please use this responsibly and have as much fun with this as I do during airsoft wars. Please also comment on the pros and cons for you and what can make it better also if you make your own I would like to see how it came out and how well it preforms.