The old flipping the coin and randomness. Sometimes you may flip and catch the coin and other times you may just let it fall to the ground.
In this video by Numberphile, Persi Diaconis is a former magician and an expert on randomness. He explains the odds of heads or tails, how magician coins differ and coin bias. He also discusses the biases that come into play that may affect the fairness of catching a coin or letting it fall to the ground.