My father has often told me of seeing a Tarzan film when he was a child where Tarzan threw some guns over a waterfall. Tarzan was obvisouly against guns and likely took the threat of some hunters and did away with them. Does anyone know what movie this was? Or did my father imagine this scene from 60 or 70 years ago?
No, your father was right. I believe it was in TARZAN FINDS A SON (1939), where Boy's guardians want to take him back to England (but not to take care of him, but rather to use him to get hold of his inheritance). They were willing to take him by force if necessary, so that's why Tarzan decided to throw their guns down a deep waterfall.
I just watched "Tarzan's Peril," the fifteenth film in the series, and it also has a similar scene where Tarzan throws rifles into a river just on the edge of a waterfall. By this point Tarzan was played by Lex Barker, instead of Johnny Weissmuller.