Apart from, you know, light bulbs.
I'll give you a sample product description, for a piece of metal you strap to your motorbike:
By placing and tuning the plates in the vehicle, the balanced ionic field created by the plates stops the decay of O2 and contamination of fuel by positive ions (Positive ions do not burn) caused by electric/magnetic fields, generated by electronics such as the alternator and high energy ignition system. The results, better air/ fuel combustion which equates to;
• Reduced emissions
• Increase power with smoother quieter running
• Reduced operating temps
• Reduced frictional drag
• Increased fuel efficiency
• Less driver fatigue due to counteracting the EMF field
Sounds great. Costs two grand.
But don't worry, for half that you can get a "lightower". "The Mini Lightower's modulated ionic field of 20km radius is also used to accelerate healing by focussing the beam of ions..."
They also have a little button for asking a question about each product, which I may use.