Liar, Liar Pants on Fire
Special thanks to Kevan Hudson and Conrad Matsumoto for reminding me of this activity.
You tell students to think of three lies and one truth about themselves. Then they tell the class each one, and students and the teacher guess if it is true or false. You can get them to write it down if they are lower level students.
This is a very fun activity and gets you away from the textbook for a bit.