A pair of Polaroid sunglasses.
Most people are unaware of their own capabilities.
Very few people know that they can detect the direction of polarisation of light with the naked eye. After all, this is how bees find their way about. If it vibrates up and down, we say it is vertically polarisecd, from side to side, horizontally. Some clever scientists used a polaroid sheet over the light in a room with bees in it. One bee was allowed to go out and find the nectar bearing flowers.