The title is misleading. When I think of someone having the "last word," I cannot help but think of a brat. A kid who always has a rebuttal, someone who can't just leave an argument finished. They have to be the top dog, and they feel like having the last word, whether it contributes to the conversation or not is none of their concern, is their way of "winning."
Recently I finished the the Autobiography of Benjamin Franklin (read it for free here as a part of Project Gutenberg). He states that he developed "the habit of expressing...[himself] in terms of modest diffidence." This is something that I have done for as long as I can remember. I prefer to contemplate my words before I let them out of my mouth. Because of this I will not be quick to respond and it may even be a long, awkward to other people, pause before I speak. I don't necessarily consider this the "last word," but I do consider it a practice of meaning what I say and forming proper sentences before I say them.
How about you? Do you prefer to have the first or last word? How do you define the "last word?" Have you read the Autobiography of Benjamin Franklin?