Blink

Billing itself as "the world's fastest game", Blink puts your pattern recognition skills to a high-speed test.

You sit across from your opponent, each with one half of the deck. Two cards are laid out in front of you, to begin two piles. You each draw three cards into your hand, and at the count of three you begin laying down matches onto the two piles.

Matches need to match only a single attribute, e.g. any red with any red, any shape with its kind, any two-spot card with any other two-spot card, etc.

The first player to run out of cards wins. The mechanic is simple enough that even very small children will enjoy this game (consider giving them a handicap of 5 or 10 fewer cards at the beginning). The brief duration of each round and its portable nature make it great for road trips, too. There's something magical about being able to challenge a friend to heated competition in the time it takes the waitress at Waffle House to get back to you with the check.