Some will say this this doesn’t qualify as a gadget because it doesn’t have electronics or use a battery, but it’s a mechanical pencil that uses liquid lead! That has to impart some sort of geeky cachet! The Liquid Graphite Technology in this mechanical pencil from Sharpie lays down the “lead” like ink. Sharpie says it’s erasable for about 24 hours, then it becomes permanent. The Sharpie Liquid Mechanical Pencil delivers the equivalent of a 0.5mm No. 2 lead. You can probably find these in local stores, and Amazon.com has them for $3.59 for one pencil and three replacement erasers.