Quizzity quizzes you on cities all over the world. To increase the accuracy of your guesses you should zoom-in on a region before clicking the map. Each round of Quizzity presents you with six city names. Points are awarded for accuracy and speed.
If Quizzity isn't for you, six other geography games can be found here.
Create Your Own Geography GameRussel Tarr's Mission Map Quest allows you to build your own geography games. Mission Map Quest is a map-based tool for creating virtual treasure hunts. The concept is simple, you create a series of clues that your students need to follow to identify places around the world. You can add as few or as many clues to your Map Quest as you like. When you're ready to have students try your Quest just give them the web address of the challenge or have them scan the QR code assigned to your Quest.
H/T to Maps Mania for the Quizzity information.