Classical armies have been replaced by Scottish clansmen and women fighting over the border between their two territories. Its fast, tactical and fun and is one of my favorite quick, portable two player games.
There is nine boundary stones lie between you and your opponent.
In front of each, you build poker-like formations of three cards on a side. Whoever plays the higher-ranking formation wins the stone. And in a unique twist, you may use your powers of logic to claim a stone even before your opponent has played all three of his cards, by demonstrating that the stone is impossible for him to win. Successfully claim five stones, or any three adjacent stones, and you win the game.