Hoax: Govt. coverup?

Who hasn't heard of ripley's believe it or not? What I want to see is personal recounts of hoaxii in order to sift out evidence of blind justice in our society.
A hoax is an attempt to trick an audience into believing that something false is real. There is often some material object (e.g., snake oil) involved which is actually a forgery; however, it is possible to perpetrate a hoax by making only true statements using unfamiliar wording or context (see DHMO). Unlike a fraud or con (which is usually aimed at a single victim and are made for illicit financial or material gain), a hoax is often perpetrated as a practical joke, to cause embarrassment, or to provoke social change by making people aware of something. per WikiPedia.
I am not interested in feats of technology or science but rather actual events orchestrated by an unknown source. Personal accounts only.