Most states make it illegal to carry such weapons. The reason for this is much the same reasoning as making it illegal to carry switchblade knives and brass knuckles & They are seen as thugs weapons, rather than as weapons of legitimate self defense.
The legality of playing casino games like blackjack for money in your own private residence can vary depending on the laws and regulations of your jurisdiction. In many places, private and social gambling among friends and acquaintances in a non-commercial and non-profit setting is allowed and not considered illegal.