The trickiest thing I ever encountered was taking an order from a guy who had an amazing stutter. It was as if he was waiting for you to react/laugh. I reasoned that from being a child people had reacted/laughed at him and that when someone didn't react abnormally it made him even more nervous so that the stutter got very high pitched. Almost like he had to make you react. Highly unusual! How to get him to communicate his feelings would be tricky in most social situations.