Altoid tin alterations are pretty popular among the hacking community, but this one takes it down in size. Using the Altoids Slim tins, Instructables user Joshua Zimmerman put together these bite-sized LED flashlights for under $5. With just a tiny bit of drilling and soldering, you could easily assemble a handful of these in an hour or two.

It falls a bit short in the "stealth" department, but you can't have your cake and eat it too, so shut up.