Backgammon
Classic. Games are short, yet interesting enough to pass an evening/night/all day. Played almost everywhere in the world, so it is also very communicative and a chat that begins with how do you say backgammon in your language can lead to funniest findings on foreign cultures (guess where the game is called puff. Hint: not in the
Puzzles
You won't take scrabble with you right? Amazing time killer in airports, train and bus stations. It is easily packed and you can even roll it into your trousers' pockets. Just remember to take more than a couple of pens and a waterproof bag.
Pen & Paper
Talking about pens: battleship, hangman, tic-tac-toe, draw caricatures of one another, I don't know whatever creativity and alcohol takes you. Like backgammon, these games are very communicative, cause everyone knows them, though in different names, and everyone has special childhood memories of them, so these are good conversation starters. And some games can be played by more 2 people.
Card games
Even if you are not into strip poker, a card deck surely will not be a burden on your luggage. In fact, if I was to take just one game along with me, it was a card deck. That's because you can play solitaire when you are alone, play stupid war games when you are a couple, and play poker or whist if you are travelling with a group of friends.
It has been short cause I'm in a hurry, back in a month. Marry Christmas all ya!