CAUTION: RWiki/1.2.3 or earlier has security vulnerability. Users of 1.2.3 or earlier are highly recommended to update to 1.2.4. 
For more detail see 
*** http://www.jin.gr.jp/~nahi/RWiki/index.cgi?cmd=view;name=RWiki ( BrokenLink )

Ruby-based, supports CGI and E-mail interface, XHTML1.0 Strict, indent-based text block format (based on RD).

Although the writing format is unfamiliar, it might not be called a WikiWikiClone...

* RWiki: 
*** http://www.jin.gr.jp/~nahi/RWiki/ ( BrokenLink )
* Download: http://www.ruby-lang.org/en/raa-list.rhtml?name=RWiki ( BrokenLink )
* Writing format:
*** http://www.jin.gr.jp/~nahi/RWiki/?cmd=view&name=RD+format ( BrokenLink )
* About RD 1: 
*** http://www.pragmaticprogrammer.com/ruby/articles/rdtool.html  ( BrokenLink )
-- Embedded Documentation in The Pragmatic Programmers, LLC
* About RD 2: 
*** http://www2.pos.to/~tosh/ruby/rdtool/en/doc/rd-draft.html ( BrokenLink ) 
-- RD working draft
----
The above wiki is not to be found, for a wiki (WAGN) written in Ruby on Rails see
*** http://en.wikipedia.org/wiki/Wagn_%28software%29