I have an English/French one.
My father was a motivational business speaker , who was addressing a French audience. As a rousing "go-get-em" type finale he wanted to say "[the people in this company] are the salt of the earth", but couldn't remember the word for "salt" so thought of the principle behind the phrase and decided the word "preservative" would do, so he said "preservatif", and was puzzled by the stunned response it received. It was later explained to him that he has just called the entire group of delagates "the condoms of the world".