Dragon Illusion Papercraft
This is a wonderful optical illusion. This little dragon is made out of paper - you simply cut it out and stick it together, and stand it on a table or window ledge. But when you move around, the dragon's head seems to follow you around the room. Have a look at the video, to see what I mean. The effect is really uncanny.
http://www.grand-illusions.com/opticalillusions/dragon_illusion/