请勿吸烟
No smoking; Please do not smoke
请勿打扰
please do not disturb
水清无鱼
lit. water that is too clean holds no fish (idiom); fig. one who is too severe has no friends
无情无义
completely lacking any feeling or sense of justice (idiom); cold and ruthless
军情五处
MI5 (British military counterintelligence office)