Being a visual artist, I love optical illusions. One that still fascinates me is the stereoscopic image.
By slightly un-focusing & crossing your eyes, you can make a pair of images overlap within your visual field to form a 3D image.
This music video for "Black is Good", by Young Rival, uses stereoscopy to achieve moving, 3-D forms out of what appears to be random static.
For best results, practice the technique on stereoscopic still images first- then watch the video in HD.
Young Rival also had another captivating video for "Two Reasons", with a series of entertaining face paintings: