What is Hamlet's last words? Why does it matter who tells his story after he dies?

"O, I die, Horatio.

The potent poison quite o'ercrows my spirit.

I cannot live to hear the news from England.

But I do prophesy the election lights

On Fortinbras. He has my dying voice.

So tell him, with th' occurrents, more and less,

Which have solicited. The rest is silence.

O, O, O, O. (dies)"

Who tells his story matters to Hamlet because it's important to him that the truth come out. He knows his reputation is ruined, but he also knows that Horatio will tell the truth.

"As thou'rt a man,

Give me the cup. Let go! By heaven, I’ll have ’t.

(takes cup from HORATIO)

O God, Horatio, what a wounded name,

Things standing thus unknown, shall live behind me!

If thou didst ever hold me in thy heart

Absent thee from felicity a while,

And in this harsh world draw thy breath in pain

To tell my story."