This project is not very useful, but it's still fun.
Step 1: Watch the Video
Click here if the link above does not work: https://www.youtube.com/watch?v=o3zlN465Ojo
Step 2: What You'll Need
You will need these tools:
_A power supply that can deliver a considerable amount of current (an ATX power supply is totally fine)
You'll also need these materials:
Step 3: The Wiring
Connect a piece of foil to the ground an a unmade paperclip to the +12 volts.
Step 4: Let's Have Some Fun!
Now, just just need to touch the edge of the foil with the paperclip and watch small plasma-arcs forming at the contact point. And if you need to cut a precisely shaped hole in a sheet of foil, this thing can even be useful! :D