Keep your money safe from these auto "extras"

Snake oil (and its corporate backers) are alive and well. The Car Connection (TCC) has complied a list of car gadgets that you should flee, not simply walk away, from:

• Deer whistle: Yes, we all want to protect Bambi (and that rabbit, for that matter.) But driving carefully when you see that “Deer Crossing” sign works instead of this device.
• Fuel system “energizer”: Better as jewelry. Bracelet or necklace? And in what color?
  
• Engine transmission “rebuild” in a can: Uh, huh. Want to worsen your car? Buy this.
• Air intake “vortex”: See “rebuild” in a can above.
• “Cathodic” rust prevention: Sure, this will work… if my vehicle drove on water or was buried under the ground.
  

What other "miracle" devices do you know that claim to increase the power of your car/keep animals safe /end world hunger, etc., that's easy, cheap and  guaranteed for the life of your car?