Flipping a coin in the air, catching it, then determining whether it has come up heads or tails is a common way to start off a game or settle a question. Because you expect that heads is as likely to come up as tails, it sounds like a fair way to make a choice.
But coin tossing isn’t really random at all. A mechanical gadget can flip a properly positioned coin so that the coin always lands showing the same face. Some magicians can make a coin come up heads on every toss—even when they don’t use a two-headed coin.