Here's an interesting thing about game design: if you take an absolutely trivial decision and add time pressure, it's no longer trivial. Rock! is a two-player game that proves the point quite nicely... by doing almost nothing else.
The deck consists of 60 cards, with each card depicting a rock, paper, or scissors. Each player takes half the deck (out of habit we usually shuffle the deck first, not that it really matters). On the count of three, each player flips the top card of their deck onto the table. It doesn't matter which card is "yours"... rather, the winner is the one to physically slap the card that would win if the two were thrown in a game of Rock-Paper-Scissors. If you slap the correct card first, you capture both cards; if you slap the wrong card (or if you slap any card when there is a tie) then your opponent captures the cards. In the event of a tie when no one slaps down, flip two more cards, winner take all. When you've played through all cards, whoever captured the most cards wins. Simple as that.
Okay, so technically the rules say that you're supposed to call out the name of the winning card. I was taught to play by slapping, and I think it's more fun that way.
At any rate, your brain does funny things when you're given such an "obvious" choice. You know that you have to come up with the right answer... and fast. This leads to your brain taking all kinds of thought-shortcuts. The game itself capitalizes on this by making the art on each card intentionally misleading: a white stone column that is clearly a rock but the color of paper, a folded-origami paper swan that might be mistaken for scissors, and so on. The end result is a game that makes you (and your opponent) look far more stupid than you actually are, and in that lies the game's genius and its stupidity.
In practice, I've found this game works well with young kids (who like the physical sensation of slapping and who are actually quite good at the game since their brains don't lock up as easily as the old fogies), and college students (who seem to get a kick out of watching their friends make morons of themselves). If you're in either group and you're looking for a game that's playable in two minutes and easily portable, go ahead and play this thing. If you're someone else, you'll probably get just as much of an interesting experience by watching someone else play this thing instead.
