When Chinese laborers built the transcontinental railway from the western side in the 19th century, they brought a traditional pain relief oil with them made from Chinese water snakes. Snake oil was an intriguing idea, and Clark Stanley saw an opportunity. He bottled his own snake oil liniment and sold it for decades. The medicine was eventually analyzed and found to consist of mineral oil, beef suet, red pepper, and turpentine. Not only was it ineffective, there were no snakes involved at all! That's how the term "snake oil" came to be used for anything fake or deceptive. For his deception, Stanley was fined $20.
There's also the story of the man who convinced people that rubbing expensive metal objects on their bodies would relieve pain, the woman who passed herself off as a princess of a fictional country, the doctor who sewed goat testicles into mens' scrotums, and other charlatans from history profiled in a list at Mental Floss.