Fast quitting and hiding!
One of the best feature that works with the "Command-tab" applications switching shortcut makes quitting or hiding many applications very easy. When I work a lot on my computer, I end up with lots of application open and after a while, it can slow down the system when you start running out of ram. The best solution to that is simply to press "Command-tab" and holding Command, you press "Q" on the application you want to quit and "H" on the apps you want to hide. With that, you can quit like ten apps by just keeping Command pressed and push "Q" ten times!