Lexicant
Players: Two or more
The players takes turns adding a letter to the beginning or end of a word stem, avoiding completing a valid word.
Description
The first player writes a letter on a sheet of paper. The players then take turns in adding a letter to the beginning or end of this stem to form part of a word, but avoiding actually completing a word. The first player forced to create a word, of at least three letters, loses.
A key part of the game is that the player adding a letter can choose to bluff that they have a word in mind. The next player can then choose to challenge them to reveal their word. If they cannot name a word, the bluffer loses; otherwise the challenger loses.
Example
In this game Blue starts with "L":

Red adds an "S", thinking of "SLOW":

Blue adds an "E", thinking of "SLED":

Red adds an "E", thinking this will force Blue to make "SLEEP" or "SLEET" and lose:

But Blue adds an "A", thinking of "ASLEEP" which will make Red lose:

At this point Red can only think of "ASLEEP", which loses the game, so bluffs and adds an "E" thinking it might persuade Blue it's something to do with "MEASLES":

Blue calls "Bluff!" and, because Red cannot name a word, wins the game.
Variations
For more variety at the beginning of the game some players say that only words of at least four letters lose the game.
Lexicant is a variant of a popular spoken word game, Ghost, in which players take turns in adding letters to the end of a stem. The player who completes a word loses. Each player has five lives, indicated by the letters of the word "ghost".
Other games like Lexicant: Scrambled Word Ladders, Word Ladders