Everyone (teacher included) has a mini-whiteboard and pen. The teacher gives a calculation or anagram and everyone starts doing it. Either set the timer or give the pupil your time plus 1 minute. When they think they have the correct answer they must hold up it up on their whiteboard. Another version involves having a grid of key terms and images, the teacher points and states a key term, if pupils think this is correct they repeat (and win a point) if incorrect they stay silent (and win a point). When pupils make an error the point is awarded to the teacher.