Most Mac keyboards have function keys along the top that, by default, do things like adjust the display brightness and sound volume.
I recently learned that if you hold down modifier keys while pressing these function keys, OS X allows you to access additional options.
If you hold down the Option key while pressing a function key, it will open the System Preferences associated with the key. For example, Option clicking on a keyboard brightness function keys (available on most MacBooks) will open the Keyboard system preference pane.
If you hold down the Shift and Option keys while pressing the display brightness up or down function keys, you have 4x the fine-tune control. The same is true for the volume function keys.
And finally, if you hold down the Shift key while pressing the volume up or down function keys, it will silence the “pop” sound it makes when during the adjustment.