"It's widely believed that a Contractor possesses a cool, analytical mind: at all times, in all situations, no matter how desperate, he's able to calculate the most logical course of action. Is it because he knows no fear? Hardly. A Contractor can get as scared as anyone. He simply doesn't let his feelings affect his reason."
Everyone has a tipping point, a Berserk Button, a threshold of shock and joy and weirdness that once crossed collapses all emotional reserve like a Fawlty Towers Plot. Some, however, have such an exceptionally high threshold that they'd probably greet the impending collapse of the universe with the same equanimity as cold tea.
Characters with Nerves of Steel are of steel in the same way a physical body can be Made of Iron — they are nigh-unshakable.
Someone who has Nerves of Steelthinks when times are tough. He makes decisions efficiently; he pushes his emotions aside, and so his decisions are not overly affected by them. He may be The Stoic, or he may be perfectly normal emotionally. Either way, his mind is never shoved aside when his emotion is. It is always thinking, a weapon as sharp as a sword. Characters with Nerves of Steel aren't intimidated by screams from those with a Hair-Trigger Temper, won't get upset if his Evil Plan is foiled (this is a morality neutral trait), he isn't likely to burst into tears when it turns out The Hero is Not Quite Dead and got better, and very probably won't even raise his voice to the man who murdered a Bus Full of Innocents unless the sound of his righteous ass kicking is loud enough to require it. Even happy news and emotions aren't likely to cause exaggerated reactions of joy (though he probably enjoys a nice hearty laugh every now and then).
Reasons for this demeanor vary. He's probably Seen It All, is naturally Spock-like, has an iron-clad Stepford Smiler facade (though on the inside they probably are banging his head against his cage) or emotionally can't be made to feel extreme emotion, such as the Tin Man. This doesn't count if the character is an Empty Shell, since there isn't anyone home to excite. The Extreme Doormat may count depending on the individual case (some are just too listless to care at all, not requiring any emotional control at all). Affably Evil villains and The Chessmaster are always composed as a result of everything going according to plan.
Even if this person doesn't have Psychic Powers; their control over their OWN brain often makes them resistant to those who do.
In short, someone with Nerves of Steel is immune to the Heroic BSOD, Villainous BSOD and Villainous Breakdown. God help us all if this proves untrue.
A good trait for a Badass Bookworm to have, at least if they want both halves at the same time. Note that nerves of steel may be hard to distinguish from Tranquil Fury at times. Showing a Stiff Upper Lip is a good way for a character to convince other people that they have Nerves of Steel. Compare Heroic Safe Mode, where the emotional/thinking part of the brain "shuts down" to allow for instinctual survival mechanisms to work unclouded by emotions. Contrast Nervous Wreck.
Nico Robin of One Piece should qualify. She's the one on the upper right not losing her cool.
Zoro and Sanji both probably count as well. Sanji's been shown to be very efficient at dealing with a rapidly crumbling situation and saving his fellow Straw Hats, Zoro never loses his cool (except at the other Straw Hats), but he's a little too happy to pick a fight with other swordsmen, and tends to consider options that are too extreme to be plausible, to qualify fully for this.
Mazinger Z: The Professor Gennosuke Yumi. Eighteen-meters-tall killer robots are advancing towards his Institute? Mount Fuji is about of erupting and burying them under burning lava? Squads of armed soldiers are besieging them under the threat of set off an earthquake under their feet if they do not surrender? A spy is aiming one gun towards him? He has been captured and is being used like hostage? It happens all the time! Basically Yumi is a scientist, hence he refuses panicking and instead of it he uses his analytical mind to study the trouble and find a solution quickly. He is so good keeping his cool he can come across like cold and aloof sometimes. Usually he only expresses emotion when one of the kids -Kouji, his daughter Sayaka or their friends- are in serious and immediate danger.
Usually you would not associate Kouji Kabuto with this trope since he is a Hot Blooded character, but he is surprisingly good keeping his coolness when he needs thinking quick to save himself or someone else.
UFO Robo Grendizer: Prof. Umon also plays this trope. He can be incredibly calm in the worse situations (or his anime version is. One of his manga versions... not so much).
To everyone's surprise, Mizuiro in Bleach turns out to have these. Faced down by a being that can literally vaporize things at the touch, he nonchalantly throws a bottle at him, then a Molotov cocktail, and expresses only mild surprise when it doesn't work.
Itachi Uchiha. Every move is carefully calculated, and he never loses his cool. That Sanity Slippage from a couple years ago? He totally faked it so Sasuke would kill him. And then after being freed from Kabuto's control when he's resurrected, he helps Killer Bee and Naruto fight the resurrected Nagato and calmly figures out how to beat Nagato's then-unbeaten gravity attack. He then, still calm, announces he's going to go defeat the resurrection technique itself.
Gendo Ikari from Neon Genesis Evangelion. He only expresses emotion when his surrogate daughter Rei is in mortal peril or about to abandon him. He calmly assesses and discusses options about the situation while his actual son might be being boiled alive, or trapped in a dimensional pit, or about to attempt to attack him with a giant robot because he's tired of his dickery. At one point he's half-coated in blood by an Angel duel happening right in front of him, and he doesn't even flinch. It's not that he doesn't care; he does, deeply. He's just... very inexpressive. There's a certain amount of self-loathing there as well.
Black Lagoon has a number of characters who are remarkably good at keeping their cool under pressure, with Chang as probably the main example. He remains perfectly calm and collected even while a psychopathic killer is trying to kill or keep him pinned down with a machine gun.
Mobile Suit Gundam Seed: Lacus Clyne. The girl is never visibly shaken by anything that happens in the series, always maintaining a calm and cheerful demeanor... even when informed that her father has been assassinated, she carries on and does what needs doing. The only time she shows any loss of control is in a private moment near the end with Kira, where she breaks down crying from everything that's happened and hugs him. One scene later and she's back to her usual unshakable demeanor.
Akagi. His inability to become scared or upset about anything eventually drives the Big Bad (whose playing style is partially based on frightening his opponents to a point where they begin to play desperately) into a Villainous Breakdown.
Charles Morse in The Edge shows impressive self-possession while stranded in the Alaskan wilderness.
Charles: You know, I once read an interesting book which said that, uh, most people lost in the wilds, they, they die of shame.
Charles: Yeah, see, they die of shame. "What did I do wrong? How could I have gotten myself into this?" And so they sit there and they... die. Because they didn't do the one thing that would save their lives.
Of course, what neither duelist knew was that their captain arranged for both guns to be empty. Everyone assumed that the 'loaded' gun, whichever one it was, had misfired. Honor was satisfied, nobody got hurt, and afterwards the captain told Horatio that while having the courage to fight a duel was good, having the sense to not fight (or start) a duel was even better.
Scheherazade in the Arabian Nights. She spends nearly three years telling story after story after story, always ending on a cliffhanger, knowing that if it isn't a good enough cliffhanger, she will be executed in the morning.
Shows up, appropriately enough, in Nerves, where nobody really loses their cool despite a breeder reactor blowing up, producing an isotope that could destroy everything within thirty miles at any moment and the one guy who knows enough to stop it going missing. Interestingly, it slightly deconstructs this trope, showing just how hard it can be to keep calm and carry on.
In the often overlooked Frank Herbert novel, The White Plague, a character takes great pain and care to describe the titular illness in its every gory, incurable, detail, knowing that no one trying to cure the white plague can possibly do so. The reason this character has such intimate knowledge of the plagues effects is because she's dying of it.
The Dresden Files: Harry Dresden is normally exhausted, bleeding, in spiritual if not physical agony, angry, terrified and running out of magic with the fate of the world on his shoulders - none of which ever stops him from thinking and finding the answers he needs.
This trope is actually deconstructed in a side story from Murphy's perspective. The fact that he is completely unfazed by everything (among other reasons) is grounds for Murphy to be worried and/or scared shitless in itself.
Multiple characters in the 1632 series — notably among the uptimers Mike Stearns and Jeff Higgins. Taking examples from the first book alone:
When Mike Stearns realizes that there are soldiers coming to attack the Abrabanel's carriage, he intentionally stands out in the open with a semiautomatic pistol to draw their fire away from the carriage — and doesn't stop firing even when one bullet rips through his sleeve.
When Jeff Higgins is defending the students in the cafeteria from a charging band of (dismounted) Croat cavalrymen, he empties his shotgun, reloads, empties it again, and — not having time to reload a second time — butt-strokes another before finally being struck down by a saber-blow.
Susan Sto Helit of the Discworld thinks logically all the time (well, nearly all the time, as everyone has their blind spots) when others wouldn't — which means both in a dangerous situation and, let's face it, most of the rest of the time too.
In the X-Wing Series, Wedge Antilles is said to alternately have cold-space lubricants and ice water in his veins. He just about invariably keeps cool and adjusts to new situations. Certainly Wedge feels emotions, some strongly, but he's well able to analyze and understand them. He's only shown losing control once - when someone uses Fantastic Racism to diss one of his nonhuman pilots, who just died to save the man, he pulls a Neck Lift and never mind that the other man is taller.
P. G. Wodehouse's Jeeves; under the most strenuous conditions, he might be prompted to elevate an eyebrow an eighth of an inch or so.
Inspector Javert from Les Misérables is a really interesting take on this. No danger can shake his cool, calm reserve: he'll arrest an armed gang with a grin and a barrage of pithy one-liners, stare down the barrel of a gun and (accurately) predict it will misfire, duck hurled paving stones, and face his execution at the hands of angry revolutionaries with equanimity. Show him mercy when he's not expecting it, though, and it's a wholedifferentstory...
In a Star Trek: TOS/Star Trek: The Next Generation/Deep Space Nine crossover novel, The Return, Dr. Bashir was doing some very delicate operation and the Red Alert klaxons went off. Data was sure that the patient was dead because the noise would have startled Bashir, but no, he kept his scalpel very still. Then he contacted the bridge. "Turn off the alarms in sick bay. I held myself still once but I don't think I could do it again."
And of course, Data does this. Though "Fiber optic nerves" would be more accurate in his case.
In Firefly, Simon Tam displays this in "Ariel". River does in "Objects in Space".
Simon operating on Kaylee in the pilot episode with (as far as he knew) the possibility that he and River might be killed or turned over to the Alliance hanging over his head.
Also, directing Zoe in operating on him in Objects in Sapce. Including warning her when he's about to pass out.
Simon is a classic Kuudere and is stoical a lot of the time. River had an even harder time in Objects in Space. She had her amygdela torn out after all and thus is flooded with emotion
Wash is able to go from the funny sarcastic guy to completely calm and in control in mere moments as well, as best seen in the Pilot in where he shows us just WHY Malcolm and Zoe have such trust in him and provides us with one of the best Crowning Moments Of Awesome in the series by outmaneuvering the Reavers without losing that stoic calm
Mr. Morden in Babylon 5. Gotta hand it to him; not even being arrested, threatened by most of the cast or coming face-to-face with Ambassador Kosh seems to unnerve him. The fact that two equally advanced aliens constantly watch over him may have something to do with that — when Londo kills/chases them off, he finally cracks.
In JAG Clayton Webb has Nerves of Steel. While he can be annoying the only picture of him panicking was in a flashback in one episode. In other times he is never fazed.
Cristina: Derek's a mess, Meredith's a mess, you're a mess - that leaves me in charge! Now go. Scrub.In.
John Watson from Sherlock. In the first episode, Sherlock mentions this trope by name while analyzing the man who shot a serial killer. At that exact moment, he catches sight of John and realizes who he's describing.
In The City Hunter, Na Na displays these. It's a necessary part of her job, as she's a professional bodyguard and government agent.
Deadlands has a character trait called nerves o' steel, but this Trope is more effectively represented by the level-headed advantage: the cool-headed hombre's lack of panic usually results in more flexibility with initiative in a combat round than others possess. Used well, a level-headed character can almost choose when to act in a round, representing a mind that is constantly looking for the perfect time to strike.
GURPS has the Unfazeable advantage, which means that the character in question never has to make Fright Checks.
The average Warhammer 40000Space Marine has the rule "And They Shall Know No Fear", which lets them regroup automatically (Provodied, of course, they haven't run of the battlefield.).
JC Denton is Deus Ex, when playing stealthily. "You mechs may have copper wiring to reroute your fear of pain, but I've got nerves of steel."
The protagonist in Metro 2033 is resistant to psychic anomalies. At least a few times in the game, he and several others are attacked by something indescribable and unnatural and he's able to resist it. This is also why he's able to withstand the Dark Ones's psychic communication without going insane.
Tales Of The Abyss has Jade Curtiss as the Stepford Smiler version of this. His ability to be unfazed by any situation is occasionally lampshaded by the younger characters as something that freaks them out.
CommanderShepard from Mass Effect, especially if you choose the Sole Survivor background. Keeping his/her cool while the rest of his/her unit panicked under attack from nightmarish Thresher Maws was what got him/her noticed enough to be considered for the Spectres. Ditto his/her feat in the War Hero origin, where Shepard effectively stared down an entire invading army until reinforcements arrived.
In Fate/stay night, Servant Archer is singled out as having these more than any other Servant due to cultivating battle experience as a way to make up for the fact that he had very few natural gifts.
Servant Assassin also has shades of this. Possibly it's due to his Extreme Doormat nature, but things like having his lungs detonated from the inside, being minutes away from death due to Mana deprivation, or being eaten alive don't seem to affect his mind much.
Chaz the talking sword form Sluggy Freelance is always ready to neutrally analyse the current situation. He being just a sword, it's not so surprising he doesn't get upset about things, although he can certainly be sarcastic.
Even in a city full of superheroes and supervillains, Skitter is an exceptionally cool customer — one particularly noteworthy occasion being her fight against Mannequin, one of The Dreaded Slaughterhouse Nine.
Jessica Yamada, introduced in Interlude 18 (Donation Bonus #3), is an unpowered therapist specializing in working with superpowered individuals, most of whom could kill her as easily as swatting a fly. Even in the face of intense fear, she maintains a calm demeanor for her patients' benefit.
The As Himself version of Doug Walker in "The Review Must Go On". His character has, to be blunt, come to life and is scaring the shit out of him by acting like some demonic abusive partner, but he only shows his terror when he's scarfing down tranquilizers alone in the car.
Rafael Nadal is an interesting example. On one hand he's fiery and celebrates when a match is going his way and thus he is not stoic like many other examples, on the other hand the man never seems to succumb to pressure, even if the match is not going in his favour. Indeed, in the world of tennis, he's often lauded for his mental strength and composure.
Pretty much any sub captain who is reasonably good. Submarine actions are very slow and unlike some types of warfare, a sub captain cannot keep himself going by mere "Fight or Flight" instinct.
Try playing professional golf without this...
Or indeed any professional sport with a large cerebral component - cricket, baseball, snooker, the aforementioned chess...
In the 23-F coup attempt in Spain, in which troops stormed the Congress of Deputies and ordered all politicians to the ground - weapons pointed at them - three of them disobeyed: Manuel Gutiérres Mellado, who stood up and ordered the leader to desist (to no avail, but took some balls) Adolfo Suarez, who remained sitting down (also took some balls), and Santiago Carrillo, who remained sitting and calmly lit up a cigarette showing Nerves of Steel and balls of the same material.
Stockbrockers are so good at this, that the US Navy considered them a background occupation of choice for Fighter Direction Officers during World War II. It was believed someone who could handle the stress of bargaining on Wall Street is likely to be good at directing air traffic in a carrier battle.
It was also about having experience in quickly allocating resources.
Michael Jordan was magic in the clutch because of these. It's really this attribute, more than his other-worldly skills and athleticism, that set him apart from all his peers. Even if he came up short, it wouldn't faze him at all next time.
An unwritten item on the essential qualifications list for commercial and military aviators, emergency responders and pretty much every other profession you can name where the smallest panic-induced mistake can cost lives.
Truth in Television: Scientists have identified a gene named COMT which has two variants, often called the "warrior" and "worrier" variants. People who have two copies of the "warrior" variant tend to exhibit this trope; their ability to concentrate, reason, solve problems, etc. actually increase when they're under stress. On the other hand, people who have two of the "worrier" variant tend to perform better than most people under normal conditions, but fold like a cheap lawn chair under pressure.