In 1941, when Dolores Moran was 15, she worked as a waitress at a drive-in restaurant in San Jose, California. One day she served a local farmer some coffee and hamburger. The next year Moran left San Jose and moved to Hollywood where she achieved brief fame as an actress.
Dolores Moran. Image source: wikipedia
By the 1960s her acting career had ended. But then, in 1968, Moran learned that the farmer she had served at the drive-in 27 years ago had died, leaving her his apricot orchard valued at around $300,000 (or $2.5 million in today's money).
Moran had no memory of serving the farmer, whose name was Anthony Ponce. Nor had the two ever communicated since then. She said, "for the life of me I can't remember the man." But evidently she had made a big impression on him.
Monroe News Star - Dec 18, 1968
Ponce's relatives contested the will, arguing that he was not of sound mind when he made it. I haven't been able to find out how the case was settled, but I'm guessing Moran got to keep the orchard since it's usually fairly difficult to invalidate a will.
If she did get to keep it, then that would have to count as one of the biggest gratuities of all time. Perhaps the biggest? Especially for an order of coffee and hamburger.
Peninsula Times Tribune - Feb 19, 1969