World's thinnest ballpoint pen...thinnest possible lines you could ever write. It's quite fine. It has some sort of special ink for reducing friction so it won't clog. It's not super-flowy like a normal gel pen but it allows you to make sharp and precise short lines, which is what I suspect it was designed to do (i.e. for writing Japanese characters (see circle in picture with writing between lines of text), or alternatively adding fine details into drawings). I think it's pretty cool.

-- Tim Hong

UniBall Signo Bit 0.18 mm Pen
8 Color Pen Set
$25
Available from Jet Pens

Manufactured by
Mitsubishi Pencil Company