Back in medieval times, writing with metallic pens was all the rage. Cool cats like Leonardo da Vinci weren't too happy carrying around quills and ink bottles, so they'd use a pen whose point was solid metal. Writing with the metal pen (called metalpoint or silverpoint if it was made of silver) was just like doing it with the ink variety, with one limiting exception: you needed specially prepared paper. No surprise, then, that metallic writing was pretty much supplanted by pencils and regular pens, even before they had Wi-Fi and scrolling LED screens.

But now modern technology has improved the technique to allow inkless pens to work with virtually any paper. This modern metal pen is made of an alloy (with no silver) that leaves marks that resemble those from a pencil, except they're permanent. Since there's no ink, the pen will never dry up or run out — though 50 years from now you may be writing with just a nub. Still, not bad for $30. Not sure if I'd want to write anyone's phone number on my arm with it, though. — Peter Pachal

Grand Illusions, via Electro-Plankton