Here is what the Ultimate Bulletin Board ( Infopop Corporation at http://www.ultimatebb.com/ ) is using. From their FAQ http://www.scriptkeeper.com/ubb/faq.html#smilies :

Smilies

You've probably seen others use smilies before in email messages or other bulletin board posts. Smilies are keyboard characters used to convey an emotion, such as a smile or a frown :(. This bulletin board automatically converts certain smilies to a graphical representation. For example, if you type in your BB post, it will automatically be converted to - a shameful face. The following smilies are currently supported:

What to Type	Emotion	Graphic That Will Appear
:)	smile
:(	frown
:o	embarrassment
:D	big grin
;)	wink
:p	razz (stick out tongue)
:cool:	cool
:rolleyes:	roll eyes (sarcastic)
:mad:	mad
:eek:	eek!
:confused:	confused

It could be done as new TWikiVariables, for example %SMILE% could be rendered as .

It even could be inserted from a select list to add an emotion to one's text.

-- PeterThoeny - 18 Feb 2000

[Just a little edit to bring this back to the top -- I like this enough to keep it from the bottom of the TWikiIceberg. -- kk 30 Jun 00] ;-)

Great idea. -- MartinCleaver - 22 Feb 2001

There is a plugin that does just this ... look at the attachments in TWikiPluginAPI ...

[they work for the first plugin implementation described there ... wait a little for the new version working with last alpha code]

-- AndreaSterbini - 22 Feb 2001

I posted the GIF files as an example. If we take this into TWiki (also Plugin) we should recreate the GIF files (because of copyright issues).

-- PeterThoeny - 24 Feb 2001

MoinMoin wiki already does something like this: /!\ results in an alert icon, and of course other effects are possible. I've seen the scheme on this page done by an irc client too.

-- DavidLeBlanc - 10 Mar 2001

NOP'd the raw smilies so they don't show as gifs

-- HeathKitchin - 05 Apr 2004

Done in SmiliesPlugin.

-- CrawfordCurrie - 11 Jan 2006