Force Quit apps from the Dock
If you right click or click-and-hold a running application in the Dock, pressing option will change the “Quit” menu item to “Force Quit.” This is especially handy for apps which have frozen but which the system hasn’t recognized as unresponsive yet. Video tag not supported. Download the video here.
Quit applications from the Application Switcher
You can quit applications from the Cmd-Tab Application Switcher by pressing “Q” on a highlighted application as you tab through them. Video tag not supported. Download the video here.
Keybindings
For advanced users, there’s a ton of fun to be had with the DefaultKeyBindings.dict file. Any combination of text actions you can complete with the keyboard can be assigned to hotkeys. See this blog entry to get started. Video tag not supported. Download the video here.
Faster folder navigation with Command-Shift-G
In Finder (and in any Save/Open dialog), you can navigate quickly to any folder by pressing Command-Shift-G to bring up the Go To Folder dialog, then typing the UNIX path to the folder. This is often faster than navigating folders by mouse, assuming you know the path. Tab completion works (fairly well), so typing the ...
Cmd-Opt-Click Dock icon to focus an app
Command-Option-Click any icon of a running app in your Dock to hide all other apps and “focus” on the app you clicked.