This is an easy way to make practicing a grammar point fun. The students play Janken and keep score of their success by growing or losing "Oni" horns. This can also be used as a warm up exercise to review previous lesson's grammar. This game is good for elementary students, junior high students and some of the more genki senior high classes.
The students are given a grammar item. Say, "Do you like baseball? - Yes I do. - No I don't." Students walk around the room and find a partner. They have a turn at saying the grammar point and then Janken. The loser gets a horn. They represent a horn by putting their left hand on their forehead and raising a finger. After each round, the students must find a new partner. When a student has five horns (all five fingers raised) they must sit down. The last person standing is the winner.
Variations include the number of horns they are allowed to grow/lose. You can control the length of the game by tweaking with this. Instead of having the kids sit down when they become an Oni, you can have them come up to one of the teachers and ask to be freed (or something). Make a note of who has to come up how many times so you can report back to the class.
Instead of gaining horns, you can have the students start out as Onis (with 5 horns) and gradually lose them until they are ready to sit down. This makes students want to do the activity faster.