I don't usually care much for these optical illusions because I've seen them all a dozen times and they are somewhat passé but here is one that I hadn't seen before that I thought was fairly cool.
Do you see the 4 small (tiny) dots arranged vertically just to the right of the heart shape? Bring your face a few inches from the screen and stare at the dots for about 30 seconds. Now look at a wall or surface with a smooth uniform color. Blink your eyes a few times and tell me who is staring back at you.