Drinking Game: Irish Snap Add to My Games
You will need at least three people for a decent game, but any amount will do. And a pack of cards.

Cut the cards up equally to each player. Play starts with the person left of the dealer. They put down the first card of their pack, turning it over as they do, and saying "two". The next person does the same, but saying "three" instead. Play goes on like this through all the card values, back to "two", and round indefinitely. This continues until the card the player puts down is the same as the value they say. For example, if the person before them says "ten", they'll say "jack". If their card is a jack, everyone slaps the pile. The last one to slap picks up the cards. And drinks a sip or shot or whatever as well.

If a player runs out of cards in their hand, they still say their number as play goes round. Except this time, the numbers stack up. For example, if you and the person before you has no cards, but the person after you does, it goes like this: say the person before you says "five", you say "six" and the person after you says "seven". This means that if the card the person after you puts down is a five, six or a seven, the pack can be slapped. Geddit?

If a player makes a slap when they shouldn't, they have to drink, and pick up the cards.

That's it, have fun!

P.S. Can be played without drink.