Non Transitive Dice
These 4 non transitive dice are one of the great illusions sold by British Toy & Magic Shop Grand Illusions, which specializes in mathematically-based novelties.
Ask a friend to choose a die, you choose another. Make ten throws, and you will win the majority of the throws. No matter which die your friend chooses, you can choose another which will beat it, even if he chooses your last “winner.” I find this baffling!
Take a look at the die layouts to see why it works: