The most emblematically uruguayan card game is called "truco", or "uruguayan truco" to be accurate. Truco means something like trick, as in: to trick someone in doing something. It's played by four or six players, in two teams of 2, or three players, with a spanish deck without the 8's, the 9's and the wildcards.
Three cards are handed to each player, and one card is left upside down under the deck, this card is called "la muestra", which would be something like "the shown" (don't worry; it makes as much sense in english as it does in spanish ;). Every player plays one card at a time in three "rounds". The game is based on betting points on each hand, and the team who wins two rounds out of three wins the hand and the pot of points of that hand (well, sort of, it's a bit more complex than that). The team to reach 40 points first is declared the happy winner.
Every card in the game has a value assigned to it, and one of the cool things about truco, is that most of the cards in the deck have one or another value depending on the "shown". All cards are given a value, some cards don't depend on "the shown", but the most valuables are the ones which do depend. This set of most valuable cards is called "las piezas" (the pieces). Remember I said it was played in teams, well, one of the funniest things about truco is that there is a language of facial signs meant to communicate what cards you have to your team mates. And part of the game skill is to communicate the cards you have without being watched by your opponents, you will try to cover your face with your arms, or wait till no one’s watching to make the signs.
Good players, and good teams are those who make the most out of the cards they have, and when they don’t really have valuable cards, they act, and trick the other team into believing that they do, and when they do have good cards they act as if they didn't laying out a trap for the other team to fall into. So there's a lot of acting involved, I guess while in poker is more natural to stay calm, and not to show emotions whatever is your hand, in truco there's a lot of team acting and outspoken speculation of the cards the other team might have. Add a bit of alcohol to the situation and you will get Shakespeare like interpretations.
The betting mechanism is based on a set of reserved words: "truco", "retruco", "vale cuatro" to raise the bet one point, and "envido" to make a special bet, or "flor" if you have a certain combination of cards. All these reserved words you just can't use them in your conversation, which sometimes does happen, being the name of the game one of the reserved words, if you do say any of them your opponents may hold the bet as made, and you will have to prove the worth of your hand of cards. One very common act is to say one reserved word and pretend it to have been a mistake, good acting is required. Another thing that is cool is to say some kind of poetic verse ending with the reserved word, to anger the opponents, typically used with the "flor" (flower), which informs the opponent team that you have a certain combination of cards that entitle you to 3 points per se.
There are a lot of subtleties to the game, like the fact that you can say any of the reserved words if you place your hand or one finger on top of the deck (for the deck not to listen), or traditions like carrying the score on a napking using squares, where each line is a point, or carrying the score with beans, and using beans to represent the amount of points in the pot of the current hand, or like licking your fingers, and wetting your forehead to place one card on it when you won the hand with the most valuable card, and fooled the other team into believing you were out of good cards, like some kind of "in your face" sort of thing.
The game is played also in argentina, the uruguyan version of the game is called uruguayan truco, or truco oriental, while the argentinian version is called "truco ciego" or blind truco, since they dont play with "la muestra", much simpler, all cards have the same value always, also much boring if you ask me. ...