Desinstalação completa do XCode
$ sudo /Developer/Library/uninstall-devtools --mode=all
Desinstale o Unix Development Toolkit do Xcode
$ sudo /Developer/Library/uninstall-devtools --mode=unixdev
Desinstalar apenas a pasta e conteúdo do desenvolvedor Xcode
$ sudo /Developer/Library/uninstall-devtools --mode=xcodedir
Desinstalar o suporte do sistema Xcode
$ sudo /Developer/Library/uninstall-devtools --mode=systemsupport
Fonte osxdaily