Rummy

Everyone is dealt from one deck: ten cards each at a table of two, seven each at three or four. One card is turned face up to start the discard pile and the rest is the face-down stock. On your turn you take one card, either the unseen top of the stock or the face-up top of the discard.

Then you lay down what you can. A set is three or four cards of the same number in different suits. A run is three or more cards in a row in one suit, with the ace low, so ace, two, three is a run and queen, king, ace is not. Melds go face up on the table, and once a meld is down anybody can add a single card to it, including a meld somebody else laid.

You finish your turn by putting one card on the discard pile. The one card you may not discard is the card you just took off that pile. The round ends the moment somebody empties their hand, and that player scores the value of every card still in everyone else's hands: an ace is one, a picture card is ten, and the rest are worth their number. If the stock runs out first, the smallest hand takes the difference instead. First to a hundred points wins.