Say The Word!
(requires paper, pencil & one envelope per player)

Setup:
Each player writes 20 words on a piece of paper. Cut the paper up so that there is only one word per piece of paper. Drop all the pieces into a cup or a hat or some such thing. After shaking up the container, each player picks one piece of paper from the hat, memorizes whatever is written on it and then seals it up in an envelope. The player then writes his or her name on the front of the envelope and keeps the envelope.

You may also want to set a time limit on the game (one day, one week, one weekend - something like that).

Play:
The goal of the game is to get at least one other player to say the word that you have sealed up in your envelope. This is not an exclusive activity. After you have your words, go about your regular business. The game is played throughout the day, tucked into the regular conversations that you normally have. As soon as you get the other person to say your word, take out your envelope and open it to show that you have just won!

Words:
Words should not be commonplace things that are said every day. For example, "the" would be a bad choice because the game would be over in 10 seconds. However, if you get too crazy with your words (like "serendipity"), you run the risk of actually picking that word and having to try to get someone else to say it.

Optional Rules:
Limit the words to being only proper nouns (like "Venice", "George Washington", or "Spiderman").
If you feel the game is too easy, instead of using words, use phrases (like "ah, Venice", "once more into the breach", or "where's my pencil?").

Cooperative Variation:
After you've mastered playing with your friends and family, try the same game but with other people.
Here's how it works:
Pick only one word (instead of a different one for each person)
The winner is the first person who manages to get someone who is not playing the game to say the word in front of everyone else that is.