Shockwave's killer app.
A Shockwave-based game not entirely unlike Pictionary. Up to ten people play a ten-round game: one person must draw pictures to signify a word, and the other players must guess it as quickly as possible. The artist has a small palette of colors and drawing tools to use, plus the all-important Clear button. Failed guesses and random observations (like "DRAW DAMMIT" and "WFT IS THAT??????????") fill the chat window and guess window in the game, but correct guesses (and "close" guesses) are not displayed to other users. Scoring is based on how early people get the correct answer relative to other players (for the guessers) and how quickly anyone gets the right answer (for the artist).
As always, the artist may not draw letters or numbers; if so, they may be punished by an administrator. If the word goes for too long without being guessed, the first few letters are gradually uncovered as a "hint." Various languages and levels of difficulty are offered, but even some of the "beginner" words are hard. Spelling counts. Sometimes, proper names are used.
If you're not behind a firewall, this is an excellent way to kill time.
How could I forget the URL? http://www.isketch.net