Bidding war

Bidding War is a card game typically involving two players. A radical variation of the classic game War, the result is not predetermined and a good player can win consistently.
Since the game does not require cards to be placed on a table, it can be played in a car or even while standing or walking, which makes it popular among travelers.
It uses a standard Anglo-American playing card deck.

Gameplay

The deck is divided evenly between the two players, giving each a face-down stack of 26 cards. Each player peeks at the top card of his/her stack. Similar to Blackjack, cards with a number 2 to 10 printed on them count as that value; the jack, queen, and king (also known as "face cards") count as 10; the ace card counts as 1.
One of the players (player A) declares his/her guess for the sum of 2 top cards (between 2 and 20). Player B declares his/her guess, which must be bigger than the first guess plus one or lesser than the first guess minus one (so if player A guessed 13, Player B can't guess 12, 13 or 14). The cards are exposed and the player closer to the actual sum receives both cards and places them face up at the bottom of his stack (the end of the "Battle").