How to uninstall XQuartz on Mountain Lion?
The instructions here are a little dated, and no longer work on Mountain Lion:
sudo rm -rf /usr/X11* /System/Library/Launch*/org.x.* /Applications/Utilities/X11.app /etc/*paths.d/X11
sudo pkgutil --forget com.apple.pkg.X11DocumentationLeo
sudo pkgutil --forget com.apple.pkg.X11User
sudo pkgutil --forget com.apple.pkg.X11SDKLeo
sudo pkgutil --forget org.x.X11.pkg
look what I found: "You may try Wineskin, but everything that uses Wine can be coimplicated to get working... As of Wineskin 2.5.6 you shouldn't need XQuartz installed at all for 10.8, as Wineskin has a custom version built in.
That said, if you ever want to use Crossover or some older Wineskin wrappers people share (like from paulthetall.com or portingteam.com), you really need to have XQuartz installed.
If you really want to get rid of XQuartz, it is NOT a self contained app, and hardly any of it is actually in the XQuartz.app bundle. You can do it multiple ways, but I'll give you the safest
Open Terminal.app and type the following...
open /opt
this should open up a Finder window showing you the contents of your /opt folder which is normally hidden. In it you'll see a X11 folder, which houses all of XQuartz. Select that X11 folder and Trash it. It'll ask for an admin password to trash it."