Round Playing Cards
Back in the day, circular playing cards were just as popular as square ones in certain places. Even nowadays you can find playing cards that come in circular formats, you just need to know where to look.
Oh, the Games We Play
Often mistaken for coasters at bars, round playing cards were built to fit more comfortably in the pocket. However, their lack of popularity directly relates to how difficult it is to shuffle them. So, take that into consideration when you're looking to make a purchase.