I run into a lot of cases where you can select some content, like error message text, but you have no menu – even a right-click context menu – for cut, copy, and paste to capture the information to use in another application like email. (Yes, you can screenshot it, but that is an ugly approach at best.) Fortunately, if you can select it or type it, you can probably use keyboard equivalents to access the clipboard without the application having had to provide any mechanism to let you do so.
To do this
I find this extremely useful, particularly in technical situations where I need to capture a crucial bit of information in order to troubleshoot a problem or submit the error to a vendor.