The Nine things Frodo wishes he had told Sam, and the one he has
The Nine he hasn't:
One (In Bag End)
There Sam was, on his knees, tears like rain in his eyes and trembling with fear (of being transformed into a spotted toad) and sorrow, a wizard's hard face near his.
"Get up, Sam!", Gandalf said, and proceeded to tell him what his punishment would be; that he'd go off with Frodo, into the unknown, places neither of them had seen, and to the Elves; to Rivendell. And Sam wept with joy, oblivious to what awaited him, to perils and loss, and to a punishment greater than becoming a spotted toad.
Frodo was staring at him, and then he felt joy as well, yet not because he would see the Elves again, not because he was oblivious, not because he was not afraid. But because he wouldn't be alone, and because there'd be a reminder of home, as pure as the Shire itself, with him wherever he'd go.
And, for later Sam would know without the words, he wishes he'd said,
"Thank you for coming with me."
Two (In the old Forest)
Cold and soothing was the water for his tired feet. There they were paddling, in the blue stream, when suddenly Frodo felt his eyes closing, half in dream already, though it was not a peaceful dream, for, which struck him as strange, he saw black not blue. Beneath him he felt something moving. And then he was screaming, yet into darkness, and naught could be heard outside, his lips stayed closed.
From far away a splash he heard, as if a stone had fallen into a bucket of water, and he was not where he'd been anymore, for beneath him there was no root, there was soil, yet above him a pressure and he screamed louder, though he did not know if anyone would hear. Till suddenly there was something, pulling, grasping him.
And he saw blue again, but of the sky this time, and then curls, a worried face, a relieved face when finally his eyes met Sam's. Frodo knew what had happened abruptly, for he was wet from head to toe, and resentful he told his gardener, who even though he did not believe him had proven to be the smarter one; had stayed away from the tree.
And, for it was true and Sam would never know, he wishes he'd said,
"You are more clever than the roots of the oldest of trees."
Three (In Lothlórien)
"The Mirror is dangerous as a guide of deeds," the Lady of the Golden Wood told Sam, who sat close beside her, with desperation in his eyes, the horrors - to him - he had just seen etched on his memory for all times and ways to come, and he covered them with his hands as if to veil them, yet Frodo was certain it did no good.
The loss of Bill by the door of Moria (to tread a path that should have been left untrodden) had struck Sam hard already, and Frodo knew what she could hear; that in his heart Sam longed to return to the Shire (after all, he'd as much as told them), where all was familiar and simple, and what he'd seen in the Mirror had reinforced this craving.
And, though there were tears in his eyes again, and his voice was wavering, he claimed, "No, I'll go home by the long road with Mr. Frodo, or not at all."
And, for it made Frodo sad as well as jubilant, he wishes he'd said,
"You have chosen me over everything you love, do you realize that? No one else ever has."
Four (At Anduin)
"Coming, Mr. Frodo! Coming!", he heard shouting a voice greatly familiar, and hope as well as an edge of desperation flamed in him, yet what followed was merely a splash. Up Frodo's head shot, and a cry escaped his lips ere as if in trance he saw the form of his dear companion - and friend - sinking. The water was swallowing him, and faster than he could think he'd grasped the paddle and made the boat swim over to Sam.
Curls between his fingers he pulled him up till he could take his hand and bring him to the safe shore, and he was relieved, though he'd been caught, though Sam was insisting he'd come with him, and his plan was ruined; he knew inside that he was fighting a losing battle while he was arguing, that Sam would not let Frodo hinder him.
And so he agreed to let him go down the most horrifying path with him; the way to Mordor. Sam got his pack and some blankets, and though this time there were words he said of thanks, though he did tell him that he was glad indeed, he also had Sam know that there were things he could not say.
For it was what he craved most, and what still he craves, though it has become impossible, he wishes he'd said,
"I do not want you to leave me."
Five (At Emyn Muil)
Never afore had Frodo seen a creature as pitiful as that which had named itself Gollum, soon covering his big gruesome eyes with thin fingers, soon staring at the hobbit's neck, where he knew his Precious, or Sméagol's Precious as he called it, hung. He wouldn't wander in the light of day but preferred the dark of night with neither stars nor moon; after all these years in the dark he must have gotten used to it.
And truly he was a deceiver, and Frodo was aware of this as well as Sam, yet there had to be good left in him, the hobbit told himself, somewhere there had to be Sméagol, for Frodo did not want to know what name he could once carry, and that there would be no going back. Also Gollum - or Sméagol - had taken an oath on the Ring of Power, and though the hobbit felt that few things he knew about this ring for certain, he had no doubts about its deceit.
So few things he could be sure of these days; so very few that he was afraid someday there would be nothing. The thought alone let all his hope fade at once, and a thick veil seemed to cloud his eyes till there was naught but darkness around him. But then there he saw a light, two eyes, a smile. And it was enough, for with that he knew then that the Ring may deceive him, that Gollum may, that even the world may cast its lot with his enemy, yet not his Sam.
And he smiled back, though weakly, and it was everything Samwise got for it, though he wishes he'd said,
"I trust you."
Six (By Minas Morgul)
Minas Morgul. A fortress as tall and dark as it was dreadful. The great, pale tower was whispering; Frodo did not understand what it was saying, but it was not speaking to him. And the Ring gave answer in its tongue, the same hisses. His shoulder was burning; so frigid it felt hot, as though it was ablaze. Yet the flames were of ice, licking the wound that was tearing at his soul; from where the Morgul blade had pierced him there was spreading the freezing cold of the Nazgûl.
The hobbit was in pain, pain greater than he could have imagined at home in the Shire, and he had lost all control over his body; it was moving, pulled by the Ring, which was growing heavier by the second, and it was trying to lead him to the tower, to the voice still whispering its inauspicious words, and it grew louder, till the whispers were screams and hisses so boisterous his ears were deaf to any noise of another kind.
There were claws at once, pulling into the other direction, away, but he found he did not want to go away, he wanted to follow the voice, for he felt only then it would stop, only then he would burn no more.
Astounded he was to find that the claws did not hurt, despite his unwillingness to follow their lead, and for merely a second the pain flew away, and he could see lips moving urgently, and he knew these lips, remembered them and there for a moment he thought he heard "Come back!" ere it was gone again, (and the pain had somehow subsided, replaced by a fascination of the great tower) yet he wishes he could have said,
"I cannot hear you anymore, but still I know the words you speak are wise. "
Seven (By Cirith Ungol)
He'd been running, he remembers, but at once there'd been a stab, like that of a knife (though not of a Morgul blade). However there'd been no pain, and there was no pain now, for there was only darkness, and in darkness one does not feel, and neither does one see, or smell, or taste.
Only hear Frodo, to his own amazement, could indeed. A voice; not that of the Ring, no, for once it did not sound like the whispers and hisses that haunted him day and night. Those were cries of battle, and despair, until softer they grew, to words, and he heard his name, "Frodo," and Sam's voice he recognized, and grief in it he heard.
And he could not tear his mouth open to reply, to tell him that he was alive, or to say what he wishes he could have said, for he knew Sam had frayed their enemy for him, ere he went unconscious.
"You are the most faithful of all companions one could have wished. "
Eight (In Cirith Ungol)
"I will not say the Day is done,
Nor bid the Stars farewell."
Frodo had heard this song long ago, to him it seemed in another life, one another had lived, one before the Ring. The Ring, which was gone, in the hands of the Enemy he supposed, and also for him all hope had been lost, and despaired he had, ere he'd hearkened the words of that song. And he squeaked, miserable, weak, afraid that merely the orcs would hear, or that he had submitted the voice.
An orc came indeed, to punish him with a whip, and blow he did once. And while the hobbit, having now given up deep in his hard, was preparing for the second strike, there was another howl of pain; not from him, but from the orc.
And suddenly there was Sam right next to him, embracing him, telling him that he'd come, and Frodo, who then thought he was dreaming, wishes he'd said,
"Your voice is that of an angel to me, and was it already when I heard your singing."
Nine (At Mount Doom)
Shivers were rattling him, from both the freezing cold of the world outside world and of that which had grasped his heart, that was making his wound burn again, and strengthening the Ring around his neck, which had grown, in seize as in weight.
No longer could he see what was before him, no longer feel the hard soil beneath him; there was only weariness, the kind one feels before he dies, and fire all around him, fire that swallowed all lands till there was darkness, and even then around him was fire, and he felt he could not move, not escape.
But still somewhere, far away, hidden, there was some will, some strength left in him, and he began to crawl, till he heard Sam's voice, that he would carry him, and clutched his back when it was there for him, yet he possessed barely the power to hold himself there, and his weakness made Sam stagger, but he did not let him fall.
And Frodo so desperately wishes he had told him,
"You are the strongest hobbit I know."
And the one he has:
The world was exploding. Everything was aflame, burning, crumbling down. And with a mixture of amazement and fright Frodo realized that this was indeed transpiring all around him, that his very own eyes were looking upon the end of all perils, of the Dark Lord Sauron, of the Ring of Power. He all but forgot about his maimed finger, for he was certain he would die here, in Mordor in fact, yet he was himself again, his heart more whole than it had been for a long time though it shall never be the same as it was afore, and at last he felt at peace. The burden, which had been hanging around his neck, was gone, destroyed.
And there was joy, joy reflected in Sam's eyes when Frodo spoke to him, and when his companion replied. The hobbits were as happy as one could be in the face of death, for the Ring had molten in the fires of Mount Doom, where it had once been forged.
And Frodo told Samwise how he was thankful for Gollum, for in the end it was his merit, and said what his heart craved to say most in that very moment.
"I am glad you are here with me. Here at the end of all things, Sam."
Disclaimer: I do not own the Lord of the Rings or any of the direct speech I have borrowed for this one shot from the chapters The Shadow of the Past (book I), The Mirror of Galadriel (book II), The Breaking of the Fellowship (book II), The Stairs of Cirith Ungol (book IV), The Tower of Cirith Ungol (book VI) and Mount Doom (book VI).