You'll need one class set of index cards, and you'll need to print the name of a famous historical figure on each one.  Have students sit in a circle facing each other.  Go around the room taping a card to each student's back.  One at a time, each student will stand in the center of the circle, slowly rotating so that his or her card can be read.  He or she then has seven yes or no questions to deduce and identify the name printed on the card.  If there doesn't seem to be enough class time to give everyone a turn, break the class into two circles.  Rewarding correct guesses with an extra point on the upcoming exam helps ensure complete participation.