My favorite is when a French colleague wanted to send some "demands" to a customer. He meant "questions", "demander" = "to ask", he didn't realize that "demand"

My favorite is when a French colleague wanted to send some "demands" to a customer. He meant "questions", "demander" = "to ask", he didn't realize that "demand" has a very different implication in English. Fortunately this was caught before he sent that email.