1. The Glico/Pineapple/Chocolate game—like hopscotch, but you can only move the number of squares that correspond to the syllables in the word you won with. (Rock is "gu" for Glico, 3 syllables; Paper is "pa" for pineapple, 6 syllables; Scissors is "choki" for Chocolate, also 6 syllables.)
2. The "acchi muite hoi" game. This one’s the best. You play your
hand, and the winner says "acchi muite hoi" and points in one
direction—up, down, right, or left. The loser has to turn his head at
the same time, and if he turns it in the same direction that the winner
pointed in, he gets a slap on the wrist.
3. The bulldog game—Win the first match, and you get to pinch one
cheek. Win the second and you get to pinch both and squeeze them up and
down, side to side, in a circle, and then pull off. If someone keeps
losing his cheeks usually end up turning bright red and very sore.
4.Green peas—the most intense of all the janken games. Tests your reflexes really well. As you throw out your hand, both of you say "green peas." (Or is it green peace? In Japanese it sounds like "gurin peesu.") The winner then gets to take the challenge to the second round by saying one of the following, depending on what you won with.
If you won with: Then say:
Rock Gurin x2
Paper Parin x2
Scissors Chorin x2
and then say the word for what you’re going to play next. Repeat the same procedure over and over with the winner calling out the next round until you reach a tie. When you tie, whoever says "don!" first is the ultimate winner. These kids in my middle school used to play this all the time. Now they’re all math geniuses. Go figure.
Here’s a random video of a bunch of dudes having a janken contest in their bathrobes.