Inkless Pen

I have no idea how well this works (or whether it's actually a con), but according to the website, this "pen" writes on most types of paper, but contains no ink.

Instead, the nib is made from some alloy that leaves a mark on the paper. Presumably, it would wear out over time, but it would definitely be a talking point until that happened.

They're currently out of stock, but you can bet I'll be ordering one as soon as they're available again.