Casio's F-91W is surely the most popular wristwatch of all time, so reliable and ubiquitous that it has never been out of production. At the height of the so-called war on terror, its use in IEDs led to it being described as a "terrorist" signifier by hysterical U.S. investigators. Though it comes in many colors and variants, there are things you can do to make your F 91W special. NODE presents interesting modifications (such as using polyimide tape to colorize the LED display) and has a shop you can buy ready-made examples. The howto videos (here's another that airport security personnel will love) double as a fascinating teardown of a classic gadget.