The Warhammer 40,000 novel The Guns of Tanith, where Scout Sergeant Mkoll survives getting his ship blown up, climbs across a half-meter-wide span over the course of a day (in acid fog and with mutant predators hounding him every way) up the side of the hab-dome which is containing the Chaos Champion he's being sent to assassinate, sneaking into his mansion, and shooting him. When the Chaos Champion reacts with disdain at the attack due to his shields, Mkoll's only response? "This is just a distraction." Followed by six tube charges blowing up in the Champion's face.
Mkoll got another one in the earlier Gaunt's Ghosts entry Ghostmaker, when he survives run-ins with multiple squads of Chaos through Guns Akimbo action despite getting increasingly wounded. This is followed up by another CMOA for the Ghosts present in Inquisitor Lilith's kill-team when they take out a Chaos force so much larger that the incident was written out of the record for being impossible.
The reason it was written out was because the kill-team, numbering a mere 60 Guardsmen, were outnumbered a minimum of 167-to-1! And they took no causalities whatsoever.
One casualty, due to a stray shot bouncing off the roof.
Colonel-Commissar Gaunt gets his very own moment in Straight Silver, where he comes across some local troops beating up his medics, who caught them stealing the Ghosts' medical supplies.
"I am Imperial Commissar Gaunt. I am known to be a fair man, until I am pushed. You have just pushed me."
At which point he shoots three of the PDF troopers dead.
Under the circumstances, I'd say he was still a fair man, even when pushed.
Really, Gaunt is pretty much a walking CMOA, as well as several other characters.
Gaunt, in Honour Guard. After the Citadel explodes he goes into depression briefly, drinking very heavily. The Lord-General Lugo, a complete idiot, comes to reprimand him, arriving one hour later. Gaunt shows up to the parade ground five seconds after Lugo arrives. The encounter goes like this:
"Lugo sniffed suddenly. 'Have you been drinking, Gaunt?' 'Yes, sir. A cup of altar wine during the morning obeisance conducted by the ayatani (Local Priests). It was symbolic and expected of me.'
Undermined a bit by the fact that he isDrowning My Sorrows, which is not exactly productive. In fact, later on, Rawne gets his own Moment by calling Gaunt out on that and demanding some evidence that he's actually making a moral stand, rather than just self-destructing in despair.
Abnett seems to favour Mkoll getting these. Even earlier in Ghostmaker, an A Day in the Limelight section reveals that he destroyed a Chaos Dreadnought singlehandedly and then tells the trooper accompanying him not to tell the others. Then in Sabbat Martyr, he out-stealths a Dark Eldar Mandrake. To quote the Scarily Competent Tracker page: "who is essentially a psychic master assassin space elf who's been tracking down and killing others like himself for centuries. Mkoll, in turn, makes him look like an amateur right before he blows his head clean off."
It is worthwhile to point out that Mkoll does say, (Paraphrased) "You're good. I'm better" and that the Mandrake was pretty overconfident.
Likewise, Mkvenner, who's badassery is second only to Mkoll, is able to fight off hordes of cultists and daemons in hand to hand combat with nothing more than an empty lasgun or wooden staff thanks to his Kung Fu skills.
MkVenner gets a supposedly posthumous one in The Armour of Contempt when he frees an entire band of resistance fighters from the goddamned Inquisition without alerting anyone.
Ana Curth gets hers when she faces down a Commissar, pulls rank on him, and basically orders him to do her bidding.
Saint Sabbat, reincarnated.
"Come, Ibram. Let us educate the archenemy of mankind." "What shall we teach them?" "The Emperor protects."
Saint Sabbat then singlehandedly destroys a Baneblade super-heavy tank with nothing but a sword and a tube charge.
Better yet, any named character that lasts longer than a page will likely get their own CMOA. There's just too many to count.
We cannot neglect Dorden, despite his being "just" The Medic. In First And Only his acting gets some Ghosts out of a tight spot. Then in Necropolis he takes out a ruffian with a nerve pinch explicitly compared to something an assassin could do.
Okay, guys, let's just admit it. Necropolis as a whole is a Crowning Novel of Awesome. You've got:
Gaunt's speech to Modile, right before he blows his head off.
The entire defense of Veyver Gate.
Gaunt and General Sturm ransacking the VPHC stockade to rescue General Grizmund.
General Grizmund's subsequent serving of the Zoican tank divisions with his Narmenian armor charge.
A short-lived Ensemble Dark Horse for this troper is Culcis of the Royal Volpone. His first appearance is in Ghostmaker, where, despite being wounded, he takes it upon himself to be the Cold Sniper in Dorden's defense of the farm. He doesn't miss, and Mkoll thinks that his eye is as good as Larkin's. He turns up again, now a Major, in Necropolis, and, during the First Storm, gets hit by the heaviest of the enemy assaults. Despite 70% casualties and the loss of his hand, he stills beats them off. Then he gets his injury seen to.
Commissar Kowle's Heroic Sacrifice while fighting Sondar's Chaos Beast by letting it bite his arms off while he was holding a belt of primed grenades.
One of the short stories making up Ghostmaker starts with the Ghosts ambushing a group of World Eater Chaos Marines ambushing an Imperial tank group. Lampshaded by the commander of the regiment they saved: "Takes discipline to ambush an ambush".
Ghostmaker can best be summed up as a series of short stories that effectively consist of "Today, this Ghost does something awesome." Today, Mkoll kills a Chaos Dreadnought. Tonight, Corbec and Dorden and a single squad of Ghosts hold off a battalion of Chaos troops to ensure a field hospital full of wounded troopers is held safe until the morning. Today, Bragg uses his status as The Big Guy to trick an entire army of brigands into emerging to get blasted by an air strike. Tonight, Caffran tricks an entire hive city of Khornate cultists into committing ritual suicide. And so on, and so forth. The novel culminates with a single platoon of Ghosts (and a squad of Eldar, but pretty much nobody knew about them) killing so many Chaos troops that Imperial High Command dismisses the entire battle as being a massive shared delusion.
Tona Criid, freshly sergeanted, beating the snot out of Cuu and refusing to let him go until he repeats her orders back politely. Then Feygor comes in to relay Rawne's request that they keep the noise down, and the conversation basically goes "Should he be bleeding like that?" "Yes." "Okay."
And in Blood Pact, Tona Criid kicks an Inquisitor holding her prisoner in the face. That same scene is also a CMOA for Commissar Blenner, a flabby, overweight officer who spends all his time in the rear, for telling off that same Inquisitor with an endless wave of witty responses.
While the whole fight with the Chaos Space Marines in Traitor General was a crowner for the entire infiltration force, Tona Criid giving one of them an explosive necklace rather stands out. Not least because her reaction to an attack by Chaos Space Marines was to attack them right back.
While he isn't killed, Corbec and Larkin managed to curb stomp Inquisitor Heldane in First and Only, who had previously been shown as an incredibly intimidating psyker far above the lowly men of the Guard.
Larkin: (after shooting Heldane in the neck) "Now we're leaving, right?"
From Traitor General, Brostin's trick with the fuel bowser is impressive. He's just gotten chastised for being a failure as a scout, then finds himself staring at a mostly-full fuel bowser with some Chaos goons around it. He sprays the fuel everywhere along the road, then
He took one last, long drag on the lho-stick, exhaled a sigh, then flicked the butt away.
It circled twice in the air.
Then two hundred metres of causeway went up in a wall of fire.
Scouts are impressed by Brostin's Heroic Sacrifice, then he stumbles out of the fire, blackened and singed, but alive. Scouts ask how he's not dead.
Brostin hesitated before replying. There had been a drum of detergent gel on the back of the bowser, retardant material carried in case of spills. Just like the stuff Brostin had used back in his days on the fire watch in Tanith Magna. He’d poured it over himself just before his trick with the lho-stick. It wouldn’t stop him burning, not in an inferno like that, but it would protect him long enough to get clear. Brostin considered explaining this to Mkoll and Mkvenner, but he realised that, for the first time, he had shown skills and secrets that impressed the unimpressable scouts. He wasn’t about to waste that moment of superiority with a mundane explanation.
He said: “I know fire. Been waging war with it for years. It wouldn’t dare harm me, not after all we’ve been through together.”
The scouts looked at him, suspecting they were being hoodwinked, but lost for an answer. Brostin clambered on up the slope.
“Come on,” he said. “We haven’t got all day.”
The tankers from Pardus also get quite a few CMOAs in the Gaunt's Ghost novel Honour Guard, showing that there are many, many Imperial Guard regiments out there that are competent badasses. In one battle, one company of Pardus tanks (numbering about 20, none of them super-heavy tanks), attacked a village held by a Chaos tank force. They expected only an equal number of enemy tanks. They ended up fighting a "division-strength" Chaos tank force (100+ tanks), plus a Baneblade super-heavy tank to boot. Nonetheless, the Pardus tankers utterly annihilate their enemy using superior tactics while only suffering moderate casualties in return. Even the Baneblade is destroyed by the company's two tank aces (each with over sixty confirmed kills) working together. As the Pardus Company Commander thought to himself at the outset of the battle: "Forget "major engagement". This is going to be historic".
Major Kleopas, commander of the Pardus tankers, would later be killed in a battle where they faced over three hundred enemy tanks. His tank was hit by an anti-tank shell, killing his crew, setting him and the tank on fire, and severing his spine below the waist. He burned to death, but not before firing one last shot that destroyed the enemy tank that had hit him.
Captain LeGuin, commander of a Pardus Tank Destroyer, also gets several CMOAs of his own. Several times, he was able to hide his massive tank destroyer so well that he fooled even Mkoll, the Ghost's chief scout. When LeGuin's tank was hit in the final battle, the Captain tried to escape his burning vehicle, only to realize that the hatch had been jammed. Grimly, the Captain sat back on his seat, and remain stoic even as he began to burn alive. Fortunately, Mkoll quickly comes to the rescue, unjamming the hatch and rescuing LeGuin. The Captain promptly ends up being featured again in another Abnett novel - Double Eagle.
Captain LeGuin was so calm and collected that he actually took the time to give his tank a proper goodbye before he bailed out of his ruined tank.
In Traitor General, the squad led by Gaunt are attacked by five Chaos Space Marines. Gaunt realises that his Power Sword might be the only weapon of use against them, readies himself to go against them, one at a time. His first kill: To sneak up on one Chaos space Marine and slices him in two with one stroke. His squad begin to achieve kills: Tona attaches their bag of Tube Charges to one, Rawne snipes one with a long las just before it can kill him, and Varl picks up a fallen bolter, and with his augmetic, produces to empty the magazine into it's face. Badass.
In Blood Pact, near the end Gaunt and his group finally arrive at a war monument on Balhaut, and his meeting with his contact is interrupted by a pair of Inquisitorial agents. They call for him to stand down, and Gaunt simply draws his bolt gun, daring them to fight. Cue the Blood Pact, Inquisitorial forces, Commisariat security troops and the Tanith First and Only engaging in a massive gun fight. To top it off when, when Handro Rime (in reality a Chaos Warlord), believes he had Gaunt cornered, he taunts Gaunt because he would never kill a man unless he thought they were undoubtedly an enemy of mankind. Cue Rawne standing right nearby, and pointing out that he would.
at the end of First and Only exploding the upper half of Fereyd's body with an esoteric chaos shrapnel gun, not just killing him but also causing Heldane to explode from the psychic backlash
In Blood Pact, while unarmed and in a jail cell still managing to disarm a Blood Pact soldier, then proceeding to smash his face repeatedly into the bars.
Killing Handro Rime
Then, in Salvation's Reach, he jumps from a walkway on top of a Shape Shifter assassin who was holding a child hostage and knifes him to death.
Also, earlier in the novel, he infiltrates a Commisariat facility just to prove a point that their security sucks. Oh, and he also happens to inadvertently interrupt an actual assassination plot at the same time.
In Salvation's Reach, three Space Marines board a Chaos Controlled space station. They face off against over three hundred Loxatl mercenaries in a single room. Entire platoons of Ghosts have trouble dealing with three!
And when they advance further into the station, intent on simply annihilating the station, which the Guard do not want since they want the Sons of Sek and the Blood Pact to believe they're starting a civil war against each other, Ludd convinces them to back down. This is a normal human, talking down a trio of genetically enhanced soldiers who take Honour Before Reason to whole new highs. Bad Ass.
The servitor piloting the Caestus should have a mention as well, piloting a heavily armed and armored shuttle and calmly ramming it directly into a Death Star-sized space station. True, the Caestus was designed specifically for that, but still, holy shit! Then when Loxatl start swarming the ship, the servitor's first (and final) response is to ram the ship even farther into the station, causing maximum damage to the enemy before he dies.
The Space Marine leading the operation, after witnessing the Caestus pilot's valiant actions, made a note to make sure that the servitor would be honored and mentioned in the Chapter's annals. High praise indeed from a Space Marine who had brushed off a Lord General Militant of the Imperial Guard at the beginning of the story.
In Ghostmaker, Gaunt, Inquisitor Lilith, and Major Gilbear of the Royal Volpones meet up with a squad of Eldar, and they are all trying to figure out what they're going to do about the horde of Chaos troops attacking the Waygate. Gilbear tosses off an offensive remark about "alien scumbags", and Eldar Dire Avenger Muon Nol raises his shrieker cannon to blast the stupid mon'keigh for his contumely. Before he fires, Gaunt tackles Muon Nol, then jumps up and decks Gilbear for being a dumbass. The awesome part is that Gaunt knocks down a heavily armed Scary Dogmatic Alien, then turns his back on him, and gets away completely unscathed.
First & Only features an extended vehicle chase where Gaunt is being pursued by troopers from a rival regiment. The chase ends with Gaunt's vehicle barreling into a barn where a large group of Ghosts are having a party. He simply leaps from the vehicle, snatches a bottle out of a trooper's hand, downs a swig of sacra and says "Lads, I could use a hand!" Then the rival troopers charge in to find EVERY GUN IN THE ROOM pointed at them.
Another from Ghostmaker. After being fired upon by allied forces that were tricked by thegeneral of the Volpone Bluebloods into thinking they were firing on cultists, Gaunt walks into the man's office. The general starts mocking him about striking the officer that fired on him, saying that's a firing squad offense. Gaunt proceeds to have the regiment that fired on them (which they had saved earlier in the chapter and had created a close bond with) drive a Basilisk (a heavy artillery piece) through the gate of the command center and point it at the window. Gaunt then makes it very clear that murder is committable and any deaths will likely be put down to the chaos of war. He then tells the general to think about that before turning and walking out of the room.