Write some numbers on the board related to the classroom.
In my particular case I had: 52, 4, 8, 3.
The Students then have to guess what the numbers mean by asking questions.
In the case of the example:
52 = number of chair legs; 4 = people wearing glasses; 8 = people in the class; 3 = Maps on the wall.
Other ideas - Numbers related to your life. Numbers related to the town / country you are in.