WP-MediaWiki adds a subset of MediaWiki markups to WordPress. 
Currently, the following MediaWiki markups are supported.
<ul>
<li>Bold</li>
<li>Italic</li>
<li>Heading</li>
<li>Lists: Besides the list markups come from MediaWiki, I also added a continuation markup such that users can put preformatted text in a list item.</li>
<li>Tables</li>
<li>External links</li>
<li>WikiLinks: the wikilink will link to Wikipedia by default, you can change the wiki site in the admin option page.</li>
<li>Table of content</li>
<li>Horizontal line</li>
<li>Preformatted text</li>
</ul>
For more information about MediaWiki markups, please refer to http://meta.wikimedia.org/wiki/Help:Editing. 
For a demo of this plugin, please refer to http://zechs.dyndns.org/wordpress/?page_id=152. 
There is also a sandbox (http://zechs.dyndns.org/wordpress/wp-content/files/wp-mediawiki/sandbox/index.php) for you to preview the effect of this plugin.

WP-MediaWiki

WP-MediaWiki is a plugin for WordPress. It adds a subset of MediaWiki markups to WordPress.

MarcusPope

Azragh

J-Ro

This plugin preserves the user-generated HTML markup in the TinyMCE editor. Unlike other plugins this one allows developers to work in the HTML tab AND end-users to work in the WYSIWYG Visual tab at the same time! No longer will your HTML markup be completely munged into an unrecognizable form when you switch between those tabs. And you don’t have to hang your users/editors out to dry when you hand off the project with a disabled Visual tab.
<h4>IMPORTANT: Please read the installation instructions carefully. If you have existing content it will not render properly after activating this plugin until you use the Fix It Tools.</h4>
(One user didn’t read or follow these steps and panicked thinking I ruined their website.)
It also supports HTML5 Block Anchor tags in addition to other HTML5 elements, something that is currently not supported in WordPress via any existing plugins.

Preserved HTML Editor Markup Plus

Preserves HTML and developer edits in HTML AND WYSIWYG tab.  Supports inline scripts/css, JavaScript code blocks and HTML5 content editing

WP-MediaWiki vs Preserved HTML Editor Markup Plus