Apple: Hide/unhide Account in Mac OS X

<< Hide users >>
sudo defaults write /Library/Preferences/com.apple.loginwindow HiddenUsersList -array-add <account name>

<< Unhide users >>
sudo defaults delete /Library/Preferences/com.apple.loginwindow HiddenUsersList


Reference:
Hide/unhide accounts in Mac OS X's login window
http://geektogeek.blogspot.com/2006/12/hideunhide-accounts-in-mac-os-xs-login.html