The "Do you want to keep the last item you copied" dialog box
Yes, it may take a fraction of a second longer for Word to exit if you decide to keep the last copied item, but not nearly as long as responding to this stupid question every time you close a Word document with something in the clipboard!
And, if you don't want to keep the last copied item, because you want to exit Word "really quickly", you still have to answer the question, which takes longer than it would have done to just keep the copied item in the first place!
Go figure!