Here is another cool gift idea for optical illusions fans. This Optical Illusion Fidget Spinner is 3D printed in PLA. It has two spinning parts that combine to produce an amazing effect. It also has 608 ZrO2 hybrid ceramic ball bearing. These spin for up to 60 seconds if the bearing is not dirty.
ViralGoods is selling these on Etsy. Make sure you choose the finish that works for you before ordering.