Scrabble

Scrabble is a long-standing board game involving words and letters. The game traces back to 1938, when Alfred Mosher Butts invented Criss-Crosswords, a game with a 15×15 board and individual letter tiles. He tabulated the frequency of various letters to determine the frequency and letter value of each tile.

James Brunot adapted the game into Scrabble and tweaked the rules somewhat, making them simpler. Although not a success at first, Scrabble allegedly gained popularity after the president of R.H. Macy’s played the game and was surprised that it wasn’t for sale in his stores. The game sold well there, and in 1952, Selchow and Righter picked up the rights to it. Since then, it has become an internationally popular game.

Typically played by two to four players, Scrabble involves a 15×15 playing board and 100 letter tiles (98 letters and two blanks). Each letter has a point value assigned to it: common letters such as E are only one point, and Z and Q are the highest at 10 points each. The blank tiles are wild, and can be used as any letter, but do not score points. The board contains squares that double or triple the value of each word and/or letter.

Scrabble has also been adapted into a well-known Game Show format for NBC. Hosted by Chuck Woolery, it simplified the rules even further and set up each word with an Incredibly Lame Pun. For more info on the game show version, go here.

Scrabble provides examples of the following tropes:

Not Cheating Unless You Get Caught: It is, technically, perfectly legal to play words that lexically don't exist — you just have to pay the penalty if you're challenged. If you can bluff your opponents into thinking it's a real word and not challenging, you're good to go. In fact, if a word is challenged but turns out to be good after all, the challenger has to pay the penalty in turn! (This last rule holds in America but is not universal - in some places there is no penalty for an incorrect challenge, or there is a 5-point penalty).
- This even works in tournaments. While in electronic Scrabble games, the computer typically won't let you play unapproved words, the judges at tournaments understand that this is a part of the game and will not point out that a word is invalid unless the word is challenged.
Perfectly Cromulent Word: This trope tends to crop up a lot if you spectate championship-level games.
Recursive Adaptation: The Game Show adaptation had its own Home Game, TV Scrabble. That’s right, a board game based on a game show based on a board game.
Score Multiplier: The bonus squares.
Scrabble Babble: Trope Maker. The old Trope Namer “Kwyjibo” is from an episode of The Simpsons where the characters are playing Scrabble
Spin-Off: Scrabble Jr. is a well-known children's adaptation.

Works that Scrabble appears in:

Film

Foul Play: Old ladies are playing through a window as the main characters pass by.

[Ethel and Elsie are playing Scrabble. Ethel has just put down the letters “fucker”, to which Elsie has added “muther” at the beginning]
Ethel: Wait, Elsie. I think you're wrong. I think you spell that word with a hyphen.

Heavenly Creatures: Pauline spells out the word PUTRID.
Sneakers: Scrabble tiles are used to solve an anagram.

Literature

Nonfiction book Word Freak covers the world of competitive Scrabble, as does the movie Word Wars.
There's a scary short story about a man who plays scrabble with his wife. Any time either of them spell out a word, that word takes place on the other person (For example, FLY causes the other person to swallow a fly or something). It ends when the man plays DEATH… The story is called “Death by Scrabble”.
In her memoir Bossy Pants, Tina Fey says that her “proudest moment as a child” was beating her uncle at Scrabble with the word “farting”.

Live-Action TV

That '70s Show: Red and Kitty are playing Scrabble with their neighbors, Bob and Midge. Red has recently discovered that Bob is bald, and he has “q-ball” on his rack. Meanwhile, Midge has “zygote” and sheepishly admits she's got nothing.
In Two and A Half Men, Alan plays online Scrabble and has played the actual game with Rose, Chelsea and one of Jake's teachers.

Chelsea: Wow. You really take this seriously don't you?
Alan: It's Like I Always Say...: The losers finish with a rack full of tiles.

In the Curb Your Enthusiasm episode “Car Periscope”, Larry plays Scrabble with an elderly man, who shocks him by putting down “coon”.
In The Sopranos, Meadow is playing with Jackie Jr. He complains that she's not allowed to play “Spanish words”. The word Meadow played was “oblique”, which he pronounces “ob-lik-ay”.

Newspaper Comics

A strip in Calvin and Hobbes has both characters playing the most outrageous words and getting ridiculously high scores from them. Another has Calvin spelling only two-letter words like “be” (complaining that he lacks vowels on his rack) whereas Hobbes wins big with words like “nucleoplasm”.

Recorded and Stand Up Comedy

Invoked in The Capitol Steps' song "76 Unknowns", about the less-well-known members of the pre-primary slate of Democratic candidates for President in the 2008 election:

Seventy-six unknowns on the campaign trail
And the lack of a message so disappoints.
Soon we'll Dennis Kucinich in
And he says that he should win
Because his name earns the most Scrabble points.

Web Comics

In this xkcd comic, which suggests use of the word “CLITORIS” without spelling it, of course.

Western Animation

Daria: The titular character adds “incarce” to “rate” in the episode “Big House”.
Metalocalypse: In the episode “Klokblocked”, Skwissgaar spells “quhzk”. To quote Toki:

Yeah, “Quhzk”s. That's whats a duck says.

In the National Film Board of Canada cartoon The Big Snit, a husband and wife are playing Scrabble. He is staring at his letters, unable to spell anything with them. A reverse shot reveals that his tiles are “EEEEEEE”.