Final Fantasy VIII contained a sub game called "Triple Triad." This game was actually sold in card form. Boosters only. 10 cards per booster. 5 game cards, 5 visual art cards. No modifications made. Now internet play has been fan-made. Only published in Japan to my knowledge.
Basically, this is a modified version of Tic-Tac-Toe. Play is on a 3x3 grid. Each player has 5 cards he does not show the other player. Cards are two-sided, one pink, one blue. Cards are based on characters and monsters from the game. There are "levels" of cards, each level containing monsters, guardian forces (summon monsters), or player characters (highest level). Each player chooses a color. Randomly determine who goes first. Place a card on the grid. Each card has a "compass rose" of 4 different numbers, 1-9, and then A representing 10. Higher levels contain higher numbers. If I place a card with the number 4 at it's north, and you place a card with a number 5 at it's south directly above mine, you "flip" mine, and both are now your color. You are trying to get the most cards to your color. You can "chain" cards too. If you flip a card, it can flip other cards. Each card is only flipped once per turn. Some cards have an elemental symbol on them, giving a +1 number bonus against anything not of that element.
The nice thing is you only need 5 cards. In FFVIII, you could actually take one of your opponent's cards they played with if you won. House rules for this type of play vary.