Here's another gas mileage rip-off, this time one I found via Daily Snopes.
This particular suspect is BioPerformance Inc., who is now trying to defend itself in court against deceptive acts and running an illegal pyramid scheme. They claimed that their pills can be dropped into a gas tank to boost mileage by 25% or more. As it turns out, the pills are actually made from the same ingredients as moth balls and toilet bowl deodorant bars. The Associated Press has the full story.
Curiously, when I was at Pep Boys today, the check-out clerk told me that someone had stopped by in a ratty old Chevy S10 and tried to sell them some of these pills. He said that they laughed the salesman out of the store, and later saw on TV how they'd been busted.