When you go out alone a lot, you develop different ways of amusing yourself. Sometimes other people get the joke, sometimes they even join in. Here are a couple you might want to try.

GAME 1: THE MOVIE LINE GAME
  Whoever you interact with (bartenders, baristas etc) try to insert lines from B-movies into your conversation.
  EXAMPLE: In a Chinese restaurant:
  Waiter: "The dumplings are very good..."
  Me: "...Obviously the product of a civilisation far superior to our own."
  EXAMPLE: Making a table reservation:
  Reservations person: "Could I have a name, please?"
  Me: "Dr Brown.... or should I say, Dr VON BRAUN."

GAME 2: THE PHONE GAME
  If there's a particularly odious person on his mobile at a table nearby, pick up your own phone and pretend to be the other half of his conversation.
  EXAMPLE: Tried it with a graduate of the 'Michael Winner Charm School' giving it 80 decibels in a wine bar one Saturday afternoon.
Winner: "I ASK YOU... AM I AN OGRE?"
Me (picks up phone): "I don't mean to say you're an ogre...'
Winner: "AND SO I SAY AGAIN... AM I AN OGRE?"
Me): "More a totally different kind of big horrifying monster, really...'
Winner: "AM I NOT ALLOWED EVEN TO SEE MY OWN CHILDREN?"
Me: "No, because you're likely to eat them and spit out their bones..."
Winner: "WE'VE BEEN HAVING THIS CONVERSATION FOR YEARS..."
Me: "I certainly agree it feels like it's lasted for years..."
And so on. 'Winner' himself never picked up on it, but both tables next to me saw the joke, and I think I brightened up their afternoons.

Game 3: SQUARES AND CIRCLES
  When out for an evening of drinking, take a pad and pencil along.
  After each drink, draw a circle on the paper, then draw a square inside the circle. Number the page and put it back in your pocket.
  When you look at the sheets of paper the next morning, the gradual change in your abilities can be extremely alarming. (This game comes from ecademist Jim Brotton, and from the look of him, if he's not a real ale fancier, he should be.)

Game 4: THE BAG GAME.
  When in a coffee shop, try to guess the contents of a specific individual's bag. Be as precise as possible, down to the titles of the books you think he or she might be reading, the brands of cosmetics, or the model of laptop.

Game 5: THE SUPERMARKET GAME.
  Most of us take a shopping list to the supermarket. However, there's a fundamental law that states you'll NEVER buy exactly what's on the list and no more. Try to do so, leaving all the stuff you forgot to put on the list until next time, no matter how much it hurts to leave the supermarket without them.