The Spinning Silhouette Optical Illusion
This is a very bizarre dancer optical illusion. At first glance the spinning lady appears to be circling in a clockwise motion. But if you look at the spinning dancer long enough - the lady will appear to change direction and start spinning counter-clockwise.
This spinning illusion has also been referred to as a Right Brain vs. The Left Brain challenge. It's a tough one and it takes a lot of focus.