The teacher prepares a list of items for revision e.g. word fields, grammar, facts. In class he/she explains the procedure. Three to five volunteers leave the classroom and wait till their turn has come. The teacher appoints a student to take the exact time and another to take down a tick for every correct answer. No repetitions! (Set up or negotiate rules on pronunciation.) Then the first player is called in.
Teacher: You have 20 second to name as many things as come to your mind.
Your topic: Parts of the body / London sights / plays by William Shakespeare / the places in a town / traffic signs / weekend shopping-list / etc.
Ready, steady, go
Once all volunteers have done their bit, award a small prize (e.g. a sticker) to the winner of the round. Then ask the class for additions before you pick the next item. Then pick the next item.