DISCLAIMER: THIS MAY BE POTENTIALLY CONSIDERED A WEAPON, AND IF YOU TRY TO DO SOMETHING REALLY, REALLY STUPID WITH THIS, LIKE BLINDING YOUR FRIENDS OR TRYING TO CIRCUMCISE THEM, IT'S NOT MY BAD, OK?
Ok, now the fun things.
Are you a Call of Duty fan and/or an office worker? If so, here is it. The office ballistic knife.
I'll make four steps: the Launcher, the Knives, the Loading and Firing, and the PSs.
Also go constructive with the comments.
Step 1: Launcher
a Pilot G2 pen
1)Disassemble the pen (note: to take off the spring, you can use a toothpick)
2)Saw off the pen tip
3)Insert in the back of the body the pieces in this order: Button, Spring, Piston
4)Screw back the top of the body