There are several unusual blackjack variations that are rarely played, such as Spanish 21, which uses a Spanish deck and offers unique rules like doubling down after splitting and bonus payouts. Blackjack Switch allows players to switch the second card between two hands, potentially creating stronger combinations. Another variant, Super Fun 21, permits doubling down on any number of cards and includes a bonus for a blackjack. These games provide intriguing alternatives for players seeking a different experience from traditional blackjack.