How can I kill a non-responding app? What are all the ways to kill a buggy GUI app?   

I can't right-click on its icon in the whatever-its-called bar, or use the top-of-window menu.  The app does not respond to anything, and does nothing but eat more and more memory as times goes on.

In Linux, there's xkill.  Is there something similar on OSX?
You can access the Force Quit dialog box by pressing &#x2318;+&#x2325;+esc, or using the Apple Menu (top left corner of the screen) and choosing Force Quit.... Select the problem app, and click the Force Quit button.



You can also kill an app using the command line (/Applications/Utilities/Terminal):

killall 'Google Chrome'


You can also use the Activity Monitor app (/Applications/Utilities). Select an app and click the Quit button:

Then, from the dialog that slides down, click Force Quit.