Shia LaBeouf wears a Bulgari Diagono X-Pro Chronograph GMT

In Transformers: Dark of the Moon, Michael Bay's 2011 third film, Sam Witwicky has saved the world twice and still cannot land a job. His girlfriend Carly works for a wealthy car collector named Dylan Gould, and at one point Gould hands Sam a watch. It is a chunky steel chronograph with a blue dial, and Shia LaBeouf wears it through the back half of the film, including a rooftop scene at sunset where he stands on the phone, rattled, the watch plain on his wrist.

The watch is a Bulgari Diagono X-Pro. Get close to it, as the film does in a tight shot of Sam's arm, and the dial reads BVLGARI in full: a polished steel case with heavy crown guards, a GMT bezel ringed with numerals, chronograph subdials, a steel bracelet. The watch press pegged it as the Diagono X-Pro chrono GMT, the sport end of Bulgari's catalog. The exact reference has never been pinned down.

Most watches in movies are there because a brand paid to put them there. This one is there because the plot needs it. The Transformers wiki, which tracks these things with more care than the studio ever did, records that the watch is the Watch-bot, a scorpion-like Decepticon spy that "transforms into a BVLGARI Diagono X-Pro." Gould, secretly working with the Decepticons, hands it to the hero on purpose, so that, in the wiki's words, "the Watch-bot connected itself to Sam's nervous system with the purpose of finding out what the Autobot's planned counterattack against the Decepticons was." In the close shots where Sam claws at his own forearm, the watch is the reason.