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