Pairs is a free print-and-play game from Cheapass Games. You can also purchase printed editions of the game at the same site. From the publisher’s description:
The Pairs deck contains only the numbers 1 through 10, in a triangular distribution (1×1, 2×2, 3×3, and so on up to 10×10). The basic goal of Pairsis to avoid getting a pair. Your odds will depend on what cards you hold, and which cards you have seen! Scoring pairs earns you points, and the first player to reach a target score is the loser.