Take a set of old Christmas cards (about three times as many cards as there are players) and cut each card into two pieces, making two sets of half-cards so that each half-card in one set has its counterpart in the other. Some of the cards should be cut so that the halves are easy to spot as belonging to each other (e.g., by cutting vertically down the middle of a colored picture of a vase of flowers), and others should be made difficult to spot (e.g., by cutting along the horizon of a seascape). Distribute one set of half-cards all over the room (they should be visible but not necessarily obvious). Give one half-card from the other set to each player and keep the "pool" in your hand. On the word "Go" all the players try to find the other half of the piece that you have given them and bring it to you. Every player finding a pair that matches is given a fresh half-card from the "pool" until there are none left. When all have finished, the group with the largest number of paired pieces wins.