If you want to remove XCode on OS X (aka Developer Tools) you can do the following:
If installed from the developer portal:
sudo /Developer/Library/uninstall-devtools –mode=all
If installed via App Store it should be:
sudo /Library/Developer/Shared/uninstall-devtools –mode=all
NOTE: To be able to install Developer Tools from the App Store, you need to delete Install XCode from your /Applications folder something like this should work:
sudo rm -Rf /Applications/Install Xcode.app
Then once you download the Xcode from the App Store, it is not installed yet. You need to go to the same place /Application/Install Xcode.app and run the installer.