CMD + OPTION + EJECT pressed for 2 seconds to put your Mac to sleep.
Use CTRL + SHIFT + EJECT to sleep just the display but leave your Mac awake
Hold down the "SHIFT" key while logging in,
to skip loading all the items you have set to "load at login" in System Preferences
Hold "CMD + OPTION" and click the desktop to hide everything but the Desktop.
Do the same for any Dock icon to hide everything but that application you click
Hold "CTRL + OPTION + CMD + 8" will invert the colors on your Mac’s display, thus obtaining a negative image of whatever is on your screen. This can prove very useful if you are outside with your MacBook and want to get rid of the polarizing effect that direct sunlight or odd angles give to an LCD screen. It will also make anything on your display a lot more legible (e.g. if you want to see certain details in a low-contrast scanned image)
CMD + OPTION + D hides / unhides the Dock. You may want to use it whenever you need more screen space
CTRL + CMD + EJECT will quickly reboot your system without displaying a confirmation dialog. Before restarting the Mac, all the applications will be quit automatically and a message will be displayed for each that will need to save information before quitting. If you press CTRL + CMD + SHIFT + EJECT to force quit any application
CTRL + EJECT is the quickest way for you to bring up the Restart, Sleep, Shutdown dialog. While this dialog is open, you can press “R” to restart the system, “S” to sleep it and “CMD + .” to cancel
SHIFT + CMD + Q will instantly log out the current account. You can also use this shortcut if you want to restrict other people’s access to your system while you are away because it also doubles as an effective system-locking tool if you have previously set a password to your account
CMD + OPTION + ESC will open the “Force Quit” dialog that will allow you to choose which application you want to force kill
Click something and hit CMD + BACKSPACE to send it to trash. SHIFT + CMD + BACKSPACE clears the trash. CMD + SHIFT + OPTION+ BACKSPACE clears the trash without asking for confirmation
