Split everyone up into groups. Give each group a massive round weather balloon (preferably filled with helium for some extra excitement!) and a couple of textas. In a time frame of about 5 minutes, each group needs to draw (and label) a world map on their balloon as accurately as possible. The group with the most accurate world map is the winner.
Important! Have information sheets prepared before hand that focus on a particular country and perhaps a missionary there. Give an information sheet to each group to discuss the country, find out about its environment, politics, issues, religion, and then pray for that country.