What version of Ruby ships with OS X 10.8 (Mountain Lion)?
On my 10.8.1 system:

/Volumes/Macintosh HD/Users/ian [ian@Ian-Cs-MacBook-Pro] [15:48]
&gt; which ruby
/usr/bin/ruby

/Volumes/Macintosh HD/Users/ian [ian@Ian-Cs-MacBook-Pro] [17:49]
&gt; ruby --version
ruby 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin12.0]