ID:90584
 
Item usage produces
\bold(\b) - \b world<<"\b I am bold. \b" I am bold.
\italic(\i) - \u world<<"\i I am italicized. \i" I am italicized.
\underline(\u) - \u world<<"\u I am underlined. \u" I am underlined.
\red - \red* world<<"\red I am red. \red" I am red.
\link(URL) - \link world<<"\link(http://www.google.com) Google \link hmm." Google hmm.

* works with \red \green \blue \white \black \magenta \cyan & \yellow

http://web.archive.org/web/20061208103304/bwicki.byond.com/ ByondBwicki.dmb?UndocumentedFeatures
*Thanks to Android Data bringing up waitfor


var/?
var/\\\\
var/\#
var/\1
var/a\ b

*Thanks to Jp for these var examples

All I we found so far, if you want to add anything to the list just comment with those 3 fields. if it produces nothing such as a hidden proc or var, give a description of it in the "produces" field.
This is similar syntax to C++. Try \n. It should give you a new line.
These aren't exactly hidden. Look through macros(text) and tags(text) in the DM reference.
Try "set waitfor" if you're looking for something hidden.
D4RK3 54B3R wrote:
These aren't exactly hidden. Look through macros(text) and tags(text) in the DM reference.

None of these are shown in either of those references.
Those are actually depreciated text macros, ever since proper HTML support was added to output they've been obsolete.
Hmm. I didn't know about that \link one.
You'll find that you can use a number of these in the chat command for some BYOND games.

My personal favourite undocumented feature is the following:
var/?
var/\\\\
var/\#
var/\1
var/a\ b