Go Fish

Deal an equal number of cards to each player (5?), and the unused cards form the stock.

On your turn, you ask for the rank of any card (AKQJT98765432), but you must have at least one card of that rank to ask (some people play that you must show the card you have when asking). Then all other players with cards of that rank must give them to you and you take another turn. (variant: you ask a specific player) If no player has such a card, they say "go fish". You draw the top card of the stock, and if it matches the rank you requested, you show it to the other players and take another turn; otherwise your turn ends. The turn proceeds clockwise. When you have all 4 cards of a given rank, they form a "book" and are displayed face up on the table. The game ends when 13 books are formed, and whoever has the most books wins. (Special case: if it is your turn, and you are out of cards but the game is not over, you draw the top card from the stock and your turn is over. This can happen after forming a book, or when another player manages to take all your cards.)

Harder version: Instead of asking for a rank, you must name a rank and suit and ask a specific player. You must still have at least 1 card of the named rank in order to ask, and must expose that card when asking. (Forcing you to show the card prevents cheating by asking for a rank you don't have.) This is similar to Happy Families[?].

The strategy is pretty straightforward. If, when fishing, you draw a rank you don't have, you should ask for it on your next turn. Otherwise, rotate among the ranks you already hold. In the harder variants, proper strategy requires remembering who has what.