Lay out all of your toys on a blanket on the floor. The submissive is on their knees.

Tell them they are to pick the toy which you are thinking about with their mouth. If they get it right they get a reward. If they pick the wrong one then punish them either with what they have choosen or with something you've choosen ahead of time.

This is a no win situation and they are in fact set up for failure. They realize this, but we both know they want it both ways so enjoy!