Disappearing Thumb

This is not actually a trick; it is something that happens due to a blind spot on your eye's retina. The effect is that the tip of your thumb disappears.

Close your right eye and hold both hands in front of you in the thumbs up position, with your thumbs touching. With your left eye, stare at your right thumb. Slowly move your left thumb away from your right thumb, keeping your thumbs at the same level. When your thumbs are about 4-6 inches apart, the tip of your left thumb will vanish from your peripheral vision.