Windows: You've hit CTRL+ALT+DEL, you've tried killing the application in Task Manager, you just can't kill it. Fire up Pskill to put that application down with surgical precision.
The appearance has changed over the years, but the window seen in the screenshot here is just a polished version of the age old "Stuff is broke" message that appears to tell you your application is not responding. Ideally, you never see it and if you do, clicking "Close the Program" will in fact close the program. What about situations where it doesn't?
Last night, I went to close an application and it refused to close. I tried all the usual tricks and helper applications to shut it down. The application was blocking an entire monitor and I had other important processes going that meant I couldn't reboot. The only tool that shut down the errant process was Pskill.
Using Pskill is simple. Pull up Task Manager or your favourite Task Manager alternative. Look for the PID number of the process you can't kill — Task Manager doesn't display it on default, you'll have to activate the column that displays the PID numbers.
Go to the command line and run Pskill with the PID number as a parameter such as "pskill.exe 9999" and the process in question will be terminated immediately. Have a favourite life-saver application? Let's hear about your favourite toolbox apps in the comments.