Caravan card

Caravan cards are items in Fallout: New Vegas.

Characteristics
Caravan cards are used to play both Caravan and Blackjack. For Caravan, players use their own decks whereas casinos usually provide the cards for Blackjack. There are six sets of Caravan cards available: a standard deck, one for each of the casinos in New Vegas and one for the Sierra Madre Casino (with the add-on Dead Money).

Obtaining a Caravan card automatically adds it to the Caravan deck in the player's inventory.

Dead Money cards
Unlike other cards, Sierra Madre cards cannot be purchased from merchants. 21 of them can be found in the Sierra Madre and its surroundings whereas the rest cannot be obtained by regular means.

Due to the fact that players do not have access to their caravan deck when in the Sierra Madre, the cards are initially not added to it and thus cannot be used when playing Caravan. Once back in the Mojave, placing the cards in a container (or simply dropping them) and picking them up again will make them available for regular use.

Behind the scenes
Two different sets of Caravan cards were given out as promotional items for Fallout: New Vegas.

Bugs

 * Cards are only viewable in the default "items" category while placing them into containers, rather than the expected "misc" category. When viewing a merchant's list of goods for sale, cards will similarly be listed only under the category with the merchant's name.
 * The game freezes when buying a large number of cards. A possible work around is to first put all playing cards you already have in the backpack of a companion. Then buy the cards you want of a vendor and finally retrieve all already owned cards from your followers inventory. This also happens when you buy two of the same card in one purchase. Another work around is just buy one at a time.
 * Continually dropping and picking up a Sierra Madre card that is required for the Dead Man's Hand challenge will eventually reward you with the challenge and XP.
 * Gomorrah's 3 of Hearts is missing a heart.