I was walking past our local pub at Uni, trying to go about my business, when a film crew was shooting a scene set ouside that pub. I was approached by the scene's director (or some person with a clipboard) and asked to walk down the street in a certain way, then was thanked for it when off camera. I guess you could call it a walk-on part. A quick search on IMDB suggests the film was "Women Talking Dirty" (I recall Elton John was involved in the production somehow) but as I've never seen the film I wouldn't know if I made the final cut. Needless to say, I was unpaid.
It was a strange year, though - that same year I was asked to take part in a police line-up. I got paid for that, though. But I digress.
A friend of mine at Uni was on Princes Street in Edinburgh when the iconic opening sprint from "Trainspotting" was shot. She was standing outside Boots.