That depends on where / how he will wear the watch. Being a mechanic, I would say go ahead and chose any mechanical watch (not a quartz watch, but one that needs to have its mainspring wound-up manually every day or so. If you're not sure how to find them, just Google "MECHANICAL WRIST WATCH".
If your friend will be wearing the watch while working at the jobsite and not keeping the watch safe in a drawer or locker, I'd say choose an IRONMAN watch made be Timex, or any of the G-SHOCK watches made by Casio. All of the IRONMAN and G-SHOCK watches are tough enough to withstand the rough treatment handed out by those who use their hands for a living. If you can afford it, another possibility is an a diver's watch worn underwater by actual divers. These, too, are built to withstand rough treatment.
And if the watch is to be worn in a rough environment, may I suggest a watch with astainless steel bracelet rather than on a leather strap which can easilt get cut or otherwise damaged.