Keyboard shortcuts are the lifeblood of many productive Mac users. Not only can they cut down on the time needed to complete a task, but they're also just plain cool. Here are 10 of the coolest, including several that most people haven't heard of.

(If you're also interested in some cool keyboard shortcuts for iPhone and iPad, Click here for our list!)

Use the keyboard combination of Command + Option + Control + Eject to instantly shut down your Mac. (And we mean instantly — make sure you've saved any open files!) This is a great time saver because it bypasses the shut-down counter that you get when using Apple menu > Shut Down (shown above). You can also put your Mac to sleep by pressing Command + Option + Eject.

These keyboard shortcuts are used to navigate around the Finder. To open the Applications folder on your Mac, press Command + Shift + A in an opened Finder window; press Command + Shift + U to open the Utilities folder; and, press Command + Shift + D to open your Desktop folder in the Finder. These keyboard shortcuts can also be used when in an opened save dialog to navigate to these folders.

When used inside of Safari, this keyboard shortcut (Command + Shift + I) will automatically generate a new email message inside of Mail.app and paste the link of the web page you were browsing in the body text. This shortcut is great for quickly sharing a website address with a friend via email.

To the bane of many Windows to Mac switchers, the Mac's "Delete" key doesn't actually function as the delete key does in Windows. The "Delete" key on the Mac instead functions as a backspace. To remedy this, you can instead use Control + D in any text area on your Mac to delete from the front of the cursor.

Use this keyboard shortcut to invert the colors on your Mac's screen. (Note: This won't work until you go to System Preferences > Keyboard > Shortcuts > Accessibility and tick the "Invert Colors" box.) This high contrast display is used by individuals with visual impairments needing high-contrast screens, but can also provide a cool effect. Warning: This keyboard shortcut may be useful when doing April fool's pranks, butMac|Life will not be responsible for any damages resulting from the prank recipient trying to beat their Mac back into shape.

When writing, we often need to quickly look up the meaning of a word; however, it can be a pain to open a dictionary and type in the word we want to look up. Instead, we prefer this nice way to quickly look up a word. With your mouse cursor over top of the word you'd like to look up, press Command + Control + D. A dialog will then pop up with the word defined by the built-in Mac OS X dictionary.

At Mac|Life, we deal with a lot of screenshots on a daily basis, and this little-known keyboard combination allows us to capture a screenshot of only the window we need. To grab just a one-window screenshot, press Command + Shift + 4, then when the crosshairs appear, press the space bar. The cross hairs will change to a picture of a camera that can be placed over top of the window to be captured and clicked. The resulting window-only screenshot will appear on your Desktop.

Sometimes when you're working on a large task, you lose track of just how many windows you've opened on your Mac. To minimize all of your opened windows and de-clutter your screen, just press Command + Option + M to have all of the windows minimized to the Dock.

Mac applications can sometimes get unruly and crash. When this happens, you can press and holdCommand + Shift + Option + Esc for three seconds to instantly Force Quit the application, and bypassing the Force Quit app.

Command + Shift + Tab is a great way to cycle through all of the different applications and windows opened on your Mac, but what if you only want to cycle through the current application's opened windows? In that case, use Command + ` (the ` is located on the key above Tab, next to the number 1). This keyboard combination will cycle through all of the opened windows in the currently active application.