Stick it in a parking meter before a really loooong night out with no worries about time expiring before you return to your car.
Place it in a Salvation Army bell-ringer’s pot at Christmas and make the evening news.
Keep it in your pocket as “mad money” in case of a sudden whim to take a 30-year round-the-world tour. (Just remember to remove the coin from your pocket before dropping off your pants at the dry cleaners.)
Buy at least 10 billion cans of soda at a vending machine.
Find a pay phone somewhere, and make a long-distance call to Mars.