Here’s one I picked up along the way and have adapted it to many grammar-based lessons as well as general fluency lessons.
I first ask if they know what a Lie Detector is. Then I explain we don’t have such a machine in the room, but will have to use our gut feelings to find out when people in the class are lying.
1. Put the learners in groups of 2-4
2. Ask them to write 10 questions they want to ask their classmates in the target tense (works well for present simple, past simple, present perfect and some modal verbs such as “can”).
3. Circulate and check the grammar, help with vocabulary as necessary.
4. Next, choose one group to choose one PERSON from the class whom they want to ask FIVE of their questions.
5. The group asks the five questions and the learner who answers must spontaneously LIE to ONE of the questions and MUST tell the truth for the other four.
6. After the five questions have been asked, the group discusses out loud which answers they think were true or a lie and as a group they decide on one of the answers they think is the lie. They ask the person who was questioned if their assumption is correct. Some learners are good liars and this part is really fun for everyone!
7. Then the next group chooses a person and the game continues. They may choose to change some questions spontaneously, which is fine (they often want to make the questions more provocative).
This exercise engages the learners on a variety of levels. As a group they create questions and decide on the grammar and vocabulary and discuss/negotiate while doing so. They write the questions and read them out loud. They listen and speak about the answers and most of all it is interesting and fun for the learners. They are not just creating language for the sake of creating language, but rather to USE it to communicate and learn. Always a winner!