Totally agreed, priorities is your personal lifesaver.
It is the only way you can get out of an argument with the eternal Get-It-Done-NOW boss. Shove the list in his face and watch him battle his own demons while he reluctantly degrades this new enormously-important-must-get-done project to the seventh or tenth place.
He will leave muttering and cursing and getting another coffee.
You will serenely return to what you were doing before the unwanted, useless interruption.
It works every time. Except if there really is something insanely urgent - but in that case, you're most likely on it already.