Escape Skype Messages to Use Special Character Combinations

You can use the new* Skype feature for doing this:

!! Preformatted text: Use two exclamation marks and a whitespace (<Space> or linebreak)
as the first 3 characters of your message and paste your snippet after it.
Example: This is (not) a kissing smiley! :*

You can also use these commands to turn this on or off:

/wikimarkup off                 // Text will not be converted.
/wikimarkup on                  // Text will be converted.

Turning conversion off (e.g. with !! ) disables the following formatting features, among others:

* bold *
~ strikethrough ~
_ italic _

and it also displays URL without formatting them to clickable hyperlinks or displaying the site's thumbnail as an image.

_{* It's available in the latest version on Windows 8 & Windows 7 (Skype version 6.22.81.105 onwards).}

As stated here, you can use either @@  (note the space after @) at the beginning of the message to override formatting, or !!  to send message in monospace font.

By wrapping parts of your message in {code} tags you can apply !! to those parts, i.e. Here is the {code}monospaced{code} word in a proportional message!

EDIT 2020: updated the link to the official FAQ, and added {code} tag description.

Since the @@ does not always work (at least it doesn't for me in Skype Web, as of Jan. 2019), you can suppress the formatting and keep the normal proportional font by inserting the special characters as HTML escapes.

E.g. using ~test~ you will see ~test~ (and not test)