Yes, I really smoke carpets.

Some stuff I made:

Extension:ExternalArticlesNg
Allows easier importing of pages from other wikis; when you load a page that doesn't exist yet it tries to pre-fill the content from another wiki.
Extension:FontAwesome2
Add Font Awesome to MediaWiki.
Extension:SaneCase
Make MediaWiki slightly less case-sensitive.
Skin:Scepticismus
MediaWiki skin designed to be comfortably readable.
Extension:Typography
Automatically use “smart” quotes, em dashes, etc.
Extension:WIGO
Add and vote for news links.