Materials: pen, paper.
Directions: First, you, the teacher, write down three things about yourself, two of which are lies. (For example: a) I have been to Japan b) I have eaten a snail c) I have ridden a horse.) Read them to the students, who then write down a, b, or c, to guess which statement is true. After everyone has guessed, reveal the true answer, and give each student who guessed correctly one point. (If no one guesses the correct answer, award the liar one or two points!)
Then, everyone has 5 minutes or so to write down three things about themselves, of which two must be lies. Have the first student read his/hers, and have everyone guess which one is true, assigning points for correct guesses as before. Then go on to the next student, and proceed until everyone has read their three statements. Students tend to really enjoy this game. I usually buy a tea or give a prize to the student or students who have the most points at the end.
To make this game much more interesting, after the student has read the 3 sentences about him/herself, allow anyone to ask that person one question (or more, if you like). This way, the student must actually try to lie convincingly, and the game lives up to its name!