Mastermind
This is based on the well-known mastermind game in which players try to crack a code. In this version, players try to crack a secret word. The game is at its strategic best for two players, but any number can play. I will describe the version for two players.
One player becomes the Master. He selects a five letter English word, and keeps it secret from the other player, the Guesser. Then the Guesser writes down a five letter word, and the Master tells him how many letters in the guessed word are present in the secret word. The Guesser's word must be a valid English word. Play continues until the Guesser gets the word exactly right, then the roles are reversed, and a new game starts.
The rules regarding telling the guesser how many letters are right are a little tricky if multiple letters are present. If the secret word is ENJOY, and the word REFER is guessed, then the correct response is `one', for the E. Position doesn't matter, and the fact that the guessed word has two Es doesn't matter, as the secret word only has one. Similarly, if REFER was the secret word, and ENJOY was guessed, the correct response would also be `one'.
If the secret word were STARE, and RATES was guessed, then the correct response would be `five', but the game wouldn't end - it would continue until the Guesser got the word right. This can be annoying, so some play that getting the five letters correct results in the game ending.