Heath Ledger wears a Casio Calculator

In the opening bank heist of The Dark Knight, the Joker robs a Gotham mob bank in a clown mask, and the watch on his gun hand is a Casio calculator watch. It is a flat rectangular digital watch with a calculator keypad set into the face, the inexpensive Casio that enthusiasts identify as the CA-53W, in production since the 1980s. Where the film puts expensive watches on its men of wealth and authority, including the Jaeger-LeCoultre on Bruce Wayne's wrist, the Joker wears a disposable digital one.

Heath Ledger died during the film's post-production, and his performance as the Joker won a posthumous Academy Award. The watch he wore for it was an ordinary calculator Casio, still in production decades later.