The most common Blackjack variations found in casinos include Classic Blackjack, European Blackjack, Vegas Strip Blackjack, Atlantic City Blackjack, and Spanish 21. Classic Blackjack is the standard version, typically played with multiple decks, where the dealer checks for blackjack and stands on 17. European Blackjack differs by dealing the dealer’s second card only after the player has completed their turn. Vegas Strip Blackjack is played with 4 decks and allows for more flexible player options, such as doubling down on any two cards. Atlantic City Blackjack, typically played with 8 decks, includes rules like late surrender and allows players to double down after splitting. Spanish 21, often seen in casinos offering a more dynamic experience, uses a 48-card deck (with 10s removed) and features special payouts and rules like automatic wins for certain 21 combinations. Each variation offers unique twists on the traditional game, making them popular choices in different casinos.