Biggest audio hoaxes

Often when people discuss audio, they talk about "snake oil" or "hoaxes."

It's pretty typical to use the term hoax as a tactic against another who disagrees with one, or holds an unusual opinion or vouches for something which has not been verified. That's not what I mean by a "hoax." 

By "hoax" I mean an audio product or claim which has been pretty definitively disproved. Maybe not to everyone's satisfaction, but to common consensus.

So -- with that definition of hoax in mind, what are some of the biggest audiophile hoaxes you've heard of?