Circulated Coins (issued by the government to be used in the community) that you find at your bank, in your change from stores, or in your piggy bank, are usually round or octagonal. If the coin came from another country, it might be round, square, triangular, or other multiple-sided coins.  If coins are non-circulating collector coins (coins you order special or buy from a dealer or at a show for example) they may have more creative shapes to look like animals, cars, motorcycles, guitars, pyramids, they may be conclave, can be puzzles, transformers, or any of a wide variety of coins.