As a computer expert, I have many spoiled hard disks. There are valuble things in a hard disk to be salvaged, like as platter, motor and magnet. I know what to do with the magnet and motor, but I usually ask myself, what to make with the platters.
They are so clean to be used as mirror, so tough to be Ninja shuriken. Aha.. I've got it!! "Circular Saw".
1x Hard disk platter
1x Hard disk spindle cap
1x CD-Rom ejection kit (DC motor, dip button, fiber)
1x Superglue adhesive
1x 30 Cm of Wire
Step 1: CD-Rom
Extract the ejection kit from the CD-Rom drive. Connect the wire to dip button and board that so the motor can be turned on and off with the button.
Step 2: Hard Disk
Extract the platter and spindle cap. Use the superglue to connect the spindle cap inside the platter and on top of the motor cap. The motor cap is removable so you can disconnect them from the motor spindle when it needed.
Step 3: Platter
Use a cutting plier to make saw blade tooth around the platter. Press each three millimeters, all in a same direction.
Step 4: Use It
Try 6~12v power supply. Actually the motor is fast enough to cut papers, plastics and thin woods, but no metals.