Rurouni Kenshin - Anti-Hero Chou lies to Kamatari that this is the latter's duty as to prevent any further suicide attempts.
Sora No Woto - Someone has to warn two armies the war is over before they start a new one. Even if it takes cutting a path through your General Ripper forces.
Dilios in 300 is ordered to return to Sparta to report what happened, using the story of Leonidas' sacrifice to rally the Greeks to stand against the Persians.
The comic-book-within-the-comic-book "The Black Freighter" in Watchmen depicts a man going to horrific lengths to get back to his town in time to warn them about the approach of the titular pirate ship and the death and violence it will bring.
Serenity: After learning the horrible truth about what happened on Miranda, Mal and the crew of the title ship set out to reach the only means of sending/spreading the report on what happened. It's something of a variant on this in that the only "authority figures" around, the Alliance, had the report buried, since they were responsible for the whole thing, but Mal is determined to get the message out in order to speak for the people who died there, and to strike a serious blow against the Alliance.
The Final Flight of the Osiris is entirely this trope. This finale to The Animatrix records the last minutes of the crew of the hovership Osiris after they discover the machines' plan to destroy Zion. While the rest of the crew fights for their lives and for every second they can spare, Jue enters the Matrix and races to a deaddrop with the information.
Star Trek: Insurrection. Dougherty actually dares Picard to send word to Starfleet; "by the time you do, this will all be done." Picard sends the ship anyway, but sticks around with an away team to stop Dougherty's plan. Something of a subversion, since the action was legally sanctioned and Picard was trying to get them to reconsider.
A common theme in stories based on Warhammer 40,000; a soldier's second most important job, after fighting the enemy, is to let those in charge know where the enemy is.
In Sandy Mitchell's Ciaphas Cain novel For the Emperor, when they discover the underground genestealers, Vail has them head back. Even after the apparent loss of all their companions, Cainnote HERO OF THE IMPERIUM!!! and Vail plug on.
In Grey Hunters, Ragnar finds some soldiers and by spying, he learns they are loyalists who are trying to discover who had landed and, if they were loyal, bring them word of where the Chaos forces are concentrated.
In James Swallow's Warhammer 40,000Horus Heresy novel The Flight of the Eisenstein, Garro learns of Horus's treachery, first on Tarvitz's word, then by seeing the weapons being armed on his own ship, then when an order to attack their own men is intercepted. He demands all his men and the officers of the ship swear an oath of moment to get the word back to Terra, and they set out to do so.
In Gav Thorpe's Warhammer 40000 short story "Renegades" Rykhel attempts this, to bring back news of his company's treachery and murders (the story ends with his traveling off into danger).
In Legion of the Damned the first part of the Space Marines' plan is to make make a Last Stand defending the only city on a cemetery world. They hope to inflict so much damage on the invading Chaos Blood Crusade that it will move on after killing the defenders and thus does not find where the women and children are hiding. The second part requires that once most of the defenders are dead at least one of the survivors fights his way out of the city and is thus able to tell any arriving Imperial forces where the women and children are.
"Passage To Dilfar", a short story in Dilvish the Damned by Roger Zelazny. The whole story is the attempt to bring the news back.
In The Shiva Option, the 4th Starfire book by David Weber and Steve White, an Alliance survey fleet finds a "back way" (an unusual warp point detectable from only one side) into one of the Bug home systems. It's a vastly easier avenue of attack than the direct route- but the fleet is already deep in enemy territory and cut off from retreat. In the end, it takes the Heroic Sacrifice of all the fleet's fighting vessels to get the survey ships home with the news.
The previous book, In Death Ground, similarly has a Terran fleet stumble upon a back door into one of the humans' home systems, which the Bugs could use to pounce on humanity at any time. They have to get back and warn Terran H.Q., but they can't use the back door to get there and have to go around the long way.
C. S. Lewis' The Horse And His Boy, part of The Chronicles of Narnia. Near the end of the book Shasta must run a long distance to warn King Lune of the invading Calormen army.
An immortal postman in Terry Pratchett's Going Postal failed at this once, causing the destruction of civilization. He's hoping time is cyclical so that he'll get another chance to deliver the message in time.
Used a little differently in J. R. R. Tolkien's universe. In an extended account of the Battle of Gladden Fields in Unfinished Tales, two men are sent back to Rivendell with the shards of Narsil alongside news that Isildur, his sons, and their whole army perished.
This is pretty much the main plot in the first book of The Serpentwar Saga. Erik and Roo ended up in the death cell and sentenced to hang. They were spared with a few others after a fake hanging to serve in Calis's band of desperate men.
The last chapter of Larry Niven's novel Protector reveals that the entire book has been one big case of Bringing News Back, telling of the human protector's war against the oncoming Pak warfleet, and giving advice on what to do should they (the human protectors) fail.
In Black Beauty, the titular horse is saddled in the middle of the night to bring the news to the doctor (who lives several miles away) that his mistress, the wealthy woman to whom he belongs, is very ill and likely dying. Understanding the severity of the mission, the horse refuses to give anything but his best in the run, not even slowing down when his groom offers to let him. Unfortunately, the doctor has no horse and must ride Beauty back to the estate, thus subverting the trope (and almost killing the poor horse).
In the first book of the Boundary's Fall series, Jeran and Dahr must bring news of Tylor the Bull's escape to King Mathis.
In the first book of Taylor Anderson's Destroyermen series, Into The Storm, Benjamin Mallory, Bristar, and Ed Palmer quickly patch a deserteed PBY and flies away from the destroyer USS Mahan to deliver enws of what happened to Captain Reddy of USS Walker.
In Andre Norton's Ordeal In Otherwhere, when Shann is captured by the Company men, Charis steals a copter to get news to Thorvald and the Wyverns. She feels quite guilty about it.
Live Action TV
An episode of Babylon 5 subverted this when they had to sacrifice a ship to give the Shadows the impression that this is what was happening. The reality was that the information they were carrying was engineered to lure them into a trap.
In Doctor Who, the Arc Words "Bad Wolf" were a message carried across dimensions by the companion Rose to warn The Doctor of the impending doom to the fabric of the universe. To produce the Stable Time Loop — they had just learned that it was significant information.
In The War Machines, Ben escapes WOTAN's slaves, despite the danger, and hurries to the Doctor to give the news — horrifying the Doctor and the man with him with his appearance.
In the Stargate SG-1 episode "2010", SG1 gets back together and form an elaborate plot to send a message through the Stargate back to 2000/1 to warn against meeting a dangerous alien race. They all try to make it to the Stargate with individual notes, but everyone except Carter is killed before they can make it; she just barely manages to get the note through the gate before being killed.
Avernum 5 has you periodically bring back news of the fugitive you're pursuing across the frontier. In a subversion, the person you're reporting to turns out to be The Mole for that fugitive.
Alyx Vance in Half-Life 2 Episode One and Two carries a data packet, in the form of a small electronic device on her belt, with plot-critical super-secret stolen data. Carrying it through a long sequence of hostile environments to where it can turn the tide of battle. Due to the bad quality of the radio communications, they can't simply transmit the data, despite sometimes establishing video communication (one can surmise it was analog).
It's implied to be the Combine intentionally jamming rebel communications.
In FTL; Faster Than Light, the player's ship travels through seven star sectors whilst being chased by a huge rebel fleet, in order to warn the Federation of the huge Rebel fleet.
The worst ending of Mass Effect 2 culminates with one character left alive to escape and tell what the party has learned to the rest of the galaxy.
A single Burmecian soldier arrives to inform King Cid of the attack on Burmecia in Final Fantasy IX. Combines with Determinator and Almost Dead Guy, since he crossed essentially the length of a continent, with the only passageway between Burmecia and his destination taken over by the enemy, and he died immediately after delivering the news.
A similar situation as above happens at the beginning of Final Fantasy XII. Vaan's older brother Reks was present when King Raminas was assassinated, supposedly at the hands of Basch. Reks was stabbed in the gut during the incident but lived long enough to testify his version of events before succumbing to his injuries some time latter.
In The Gamer's Alliance, when the Battle of the Rivers turns out badly for Alent's Western Army thanks to the Coalition's surprise attack, the commander orders one of his soldiers to flee to Alent to warn the Council of Mages about an impending Coalition invasion while the rest of the soldiers try to hold back the overwhelming Coalition army.
In the Justice League season finale "The Savage Time", the League learns that Vandal Savage is leading the Nazis to invade the United States. As they lack any means of radioing this information, the Flash runs across the Atlantic to warn the US.
Mulan: Shan Yu lets two captured soldiers go just so they can deliver the message of his coming to the Emperor. And just to show how cruel he is...
Shan Yu: How many men does it take to deliver a message?
Archer: (aiming) One.
Subverted in a way by General Grievous in Star Wars: The Clone Wars. His first public appearance was during the Battle of Hypori, at which he single-handedly defeated a team of seven Jedi, killing four of them and definitely about to kill the other three had an ARC team not intervened and held him off. In fact, he had been active since the Battle of Geonosis, four months prior - he simply never left any Republic forces alive to tell of his existence.
Just before the Battle of Marathon between Athens and Persia, the Athenians sent a soldier named Pheidippides to warn Sparta that the long-feared Persian invasion had begun, and request Spartan aid. He ran 149 miles to Sparta on foot, then ran back to Athens with the bad news that Sparta would not help them for a week. Supposedly he arrived only a few days after he'd left. This was in 490 BCE.
A later, inaccurate legend has Pheidippides run 26 miles from Marathon to Athens after the battle, to let them know that Athens had won and nobody should strike a deal with the Persians. Upon arrival in Athens, he shouted, "nenikékamen!" ("we are victorious!") and promptly dropped dead from exhaustion.note People run marathons non-stop routinely these days, and very few die, but then most of them hadn't just fought a battle.
This inspired and named the tradition of running marathons.
The midnight rides of Samuel Prescott, William Dawes, and Paul Revere. The last of these only made it to one village before he got caught, but he got the poem, so he's the famous one.
Terasaka Kichiemon the only survivor of The Forty Seven Ronin was told to bring word of their successful raid to Ako. After the other 46 committed suicide he alone was pardoned by the emperor. When he died at the very old age of 87 he was buried with the others.
Laura Secord is the Canadian version of Paul Revere - after hearing plans of an American surprise attack, she travelled over 32km (from behind enemy lines, too) to inform British soldiers of the attack. The attack met disaster.
During the absolute Curb-Stomp Battle that was the Battle of Cannae, one of the Roman consuls, Lucius Aemilius Paullus, was gravely injured. Offered a horse to flee the battle by Cornelius, one of the few surviving tribunes, he responded thus:
Long may you live to do brave deeds, Cornelius, but do not waste in useless pity the few moments left in which to escape from the hands of the enemy. Go, announce publicly to the Senate that they must fortify Rome and make strong its defence before the victorious enemy approaches, and tell Q. Fabius privately that I have ever remembered his precepts in life and in death. Suffer me to breathe my last among my slaughtered soldiers, let me not have to defend myself again when I am no longer consul, or appear as the accuser of my colleague and protect my own innocence by throwing the guilt on another.