OK Try This

While sitting in your chair lift your right foot up and make continuous clockwise circles with it. Now in the air with your right hand write the number 6. Can you keep up those clockwise circles?

OR

Read this text out loud as fast as you can

"Acocdrnig to an elgnsih unviesitry sutdy the oredr of letetrs in a wrod dosen't mttaer, the olny thnig thta's iopmrantt is that the frsit and lsat ltteer of eevry word is in the crcreot ptoision. The rset can be jmbueld and one is stlil able to raed the txet wiohtut dclftfuiiy."

Now read this text again, paying attention to each word and you'll probably notice "some" typing errors ;)

OK one more fun one, can you spot the face?
Once you've spotted it once it will jump out at you every time you look at it.