One of the most popular digital wristwatches, the Casio F-91W is a favoured by terrorists and militaries. A very affordable and durable wristwatch, even celebrities and politicans wear it. This article from Vice.com explains why perhaps this is the most famous watch of all time... "Ripley wore a Casio F-91W in Alien, as did Obama before he became the president of the United States. Apparently, it’s also the only branded thing Osama bin Laden ever wore in public.