The F-91W has been in continuous production since 1989, virtually unchanged, and has sold well over 100 million units — making it arguably the best-selling watch of all time. Urethane resin keeps the whole thing at 21 grams, light enough to forget entirely, while the digital display packs in a stopwatch, alarm, and full calendar without ever feeling cluttered.

Its battery is rated for seven years and frequently outlasts that, and the module inside — Casio's 593 — has stayed the standard reference for restoring and modding these watches decades after release, simply because nothing about the design needed fixing.