Not exactly what you asked for, but here is an alternative that I've found handy.
- Type Ctl + Alt + t to bring up a terminal.
- Type this command in the terminal:
xkill
(Your cursor will change from an arrow to an X.) - Use the cursor to click on the application window that you want to terminate. That application will immediately be killed.
Notes:
- This command will kill whatever you click on while the cursor is an X. (I.e. Don't click on your desktop!)
- If you decide not to kill anything, type Ctrl + c to cancel the xkill command.