The gift in this sentence is the O. It changes the subject, it takes everyone’s attention.
I mean – it depends on the production. The O could be a simple, reaction to the news that Norway and England have arrived and are greeting each other with war sounds. O. I see.
Or the O could rise up from a pain in his body. It could surge out of his guts and through his mouth as he realizes, more acutely now that the end is moments away.
Or he could be suddenly seeing the ghost of his father beckoning him to the other side. Or flights of angels waiting to receive him.
There is a conversation about Hamlet’s end that features some Os at the end of this speech – those Os are not featured in this edition – but there are a lot of possibilities and the way that Hamlet senses the death that awaits him is significant. It could be physical. It could be spiritual. It could be visual. It is full of possibilities.