The login screen of OS X by default only shows the computer name. It is however possible to add a message or warning to the login screen. Use following command to do this.
10.6
Disable support for radio stations (streams) in iTunes
Disable support for Radio Station (streams) within iTunes 7.1+. After applying this command the option ‘Radio’ will disappear in the navigation bar and the Advanced menu options.
Disable ‘Connect to server’ menu option in OS X Finder
Disable the menu option: ‘Go ▸ Connect to server…’ (cmd⌘ + K) in the Mac OS X Finder menubar.
Disable ‘Home Sharing’ options in iTunes
Disable the Home Sharing functionality within iTunes 7.1 or above. After applying this command the option ‘Home Sharing’ will disappear in the navigation bar and the Advanced menu options.
Show icons from hidden application translucent in OS X Dock
In Mac OS X you can hide an application with the key combination cmd⌘ + H. That the application is hidden you can not see directly in the Dock. Using this command, hidden applications are displayed with a translucent icon in the Dock:
Enable the Safari debug menu
Safari has a hidden Debug-menu that offers some options for debugging the browser. The debug menu is different from the Developer menu. You can perform load and stress tests en additional logging features.
Change default Mac OS X screencapture file type
Specify what file format you want to use for your screenshots (shift⇧ + cmd⌘ + 3) under Mac OS X. Th default format is .png, there are a lot of additional file formats available: png, pdf, tiff, pict, jpg, bmp, gif, psd, sgi and tga.