This is so cool, it will boggle your mind. Like me, you will probably keep trying at least 50 more times to see if you can outsmart your foot, but you can't.
While sitting at your desk, lift your right foot off the floor and make clockwise circles.
Now, while doing this, draw the number "6" in the air with your right hand.
Your foot will change direction and there's not a thing you can do about it.
Probably been done before, but what the heck.