The folks over at Moletech sell a typically nonsensical mileage enhancing product called MTech which uses the magic of molecules and ions (and science!) to magically increase the fuel efficiency of your vehicumobile. I could write for hours about the product, but I'll skip it because even if it did work, they screwed up on their stock photography.
Moletech sells MTech according to the type and displacement of the engine in your car: the bottom rung is the version for gasoline-powered vehicles under 3.0L of displacment. The only problem is that the photography they used is for the Porsche 997, which is only sold in 3.6L and 3.8L variants. Oops.
I spotted this in a SkyMall catalog earlier today. Surprised?
Bonus: doing the followup web work for this post I found their installation guide (PDF) which instructs unwitting customers to drop big metal slugs into their gas tank (page 8) and to drill holes into their air box (page 12).

Hah, I saw this in Skymall myself and had similar thoughts. Good post.
The installation guide is what really got me. I was halfway tempted to not post this until I read all the way through that.
Yowza.
--D
Doesn't everybody know that cars crave Brawndo: The Gas Mileage Mutilator. It has electrolytes.