"Who cares about decent? The game, Mrs Hudson, is on!"
Allergic to Routine: Sherlock has a need for intellectual stimulation that strongly brings to mind a drug addict's desire for the stimulant of their choice, and repeatedly goes to dangerous lengths in order to avoid becoming bored - a trait he shares with his arch-nemesis, Moriarty. However, possibly as a means to complement Sherlock, this particular version of John Watson is heavily hinted to be an adrenaline addict and a thrill-seeker.
All of the Other Reindeer: In addition to being hated by pretty much the entire police force sans Lestrade, in "The Blind Banker", it is revealed that all his classmates hated him back in school too.
A Man Is Not a Virgin: Averted. Sherlock claims in the very first episode that neither girlfriends nor boyfriends are his area and he considers himself married to his work. In Season 2, it's explicitly stated that he is a virgin. But in response to speculation about Sherlock's asexuality, creator Steven Moffat has noted that he is, in fact, heterosexual, but has a "monk-like devotion to celibacy," while hinting that said devotion may change as the series progresses.
John is in disbelief that Sherlock has apparently never had a "girlfriend, boyfriend, a relationship of some kind, ever."
Moriarty's nickname for Sherlock is "The Virgin".
Even Mycroft mocks his brother:
Sherlock: Sex doesn't alarm me. Mycroft: How would you know?
Ambiguous Disorder: Sherlock shows many classic signs of Asperger Syndrome, including limited empathy, abnormally intense interests and idiosyncratic language, but classifies himself as a high-functioning sociopath who lacks emotion (whereas Asperger's Syndrome is characterized by very strong emotions). John occasionally teases about possible diagnoses for his friend. He also claims to be a high-functioning sociopath while others think he's a psychopath based on his overall personality.
Lestrade: I suppose he likes having the same faces back together. It appeals to his... his... John: [snarkily] Aspergers?
Berserk Button: The normally calm Sherlock doesn't take anyone hurting or insulting Mrs Hudson well. He throws the CIA agent in Scandal out a second-story window... five times... for touching her.
Break the Haughty: The plot of "The Reichenbach Fall", where Moriarity uses Sherlock's jerkass pride in his work to slowly destroy the detective's life.
Brilliant, but Lazy: Zig Zagged Trope. If he thinks it's worth his while he'll run several blocks, break into private property, or lie and cheat to get information. If he doesn't, his level of laziness has to be seen to be believed:
In "A Study in Pink", won't lift his hand about three inches to grab the phone John offers him, forcing John to actually place it in his palm.
In "The Great Game", while fiddling with instruments, Sherlock asks Watson to hand him his phone, which is in his jacket. The one Sherlock's wearing.
In "A Scandal in Belgravia", gets John to skype him a view of crime scene because he doesn't want to get out of bed. Then can't be bothered to get dressed when summoned by the Queen.
Brutal Honesty: Sherlock's M.O. Used in several settings — one time he might comically extort someone with sensitive information, the other John chews him out for being rude and tactless.
Byronic Hero: Embodies all of the major traits of this trope.
Celibate Hero/Celibate Eccentric Genius: Sherlock considers himself married to his work, though that doesn't stop an intense - but brief - relationship from blossoming between him and Irene Adler in A Scandal in Belgravia, the exact romantic/sexual nature of which is not discussed; and then there's the Ho Yay between him and John Watson that certain fans claim to see all over the place (and which is occasionally referenced in-universe to John's annoyance).
Steven Moffat: It's the choice of a monk, not the choice of an asexual. If he was asexual, there would be no tension in that, no fun in that – it's someone who abstains who's interesting. There's no guarantee that he'll stay that way in the end – maybe he marries. Mrs Hudson. I don't know! (The Guardian, Jan 20th, 2012)
Moffat posits in the same interview that Sherlock dismisses the charms of women because he finds them a distraction, and that he would not be living with a man if he fancied men.
Genius Ditz: He's incredibly smart, but Book Dumb in areas that don't interest him. For instance, he can't name the Prime Minister and doesn't know the Earth goes around the Sun.
Glad He's On Our Side: His sociopathy, his despising being bored, and his being Not So Different from Moriarty are frequently brought up, as well as how awful of a prospect it would be if he stopped helping the police and ended up committing crimes for thrills himself.
Good Is Not Nice: As he tells Moriarty in "The Reichenbach Fall", "I may be on the side of the angels, but don't think for one second that I am one of them."
Grammar Nazi: Deliberately corrects the grammar of a prisoner in Minsk at the start of "The Great Game" to make the man confess to murdering his girlfriend.
Called "Hatman" by the press, due to wearing a deerstalker to hide his face.
"The Reichenbach Hero" for his most famous case to date.
"Sir Boasts-A-Lot", which Moriarty alludes to while telling a fairytale.
Insufferable Genius: He really can't help himself, not even after getting tossed out of a courtroom where he's the star witness and into a prison cell for showing off.
Intelligence Equals Isolation: Zig Zagged. It's hard to say what came first, Sherlock's incapacity of social interaction, or his aversion of it. Although Mycroft seems to have encouraged distance to others, his friendship with John proves that he is neither above nor averse to relationships with other people as long as it does not hinder his work.
Sincerely apologizes to Molly after offending her in "Scandal"; John is visibly shocked.
Fantasizes about all the ways he could kill the CIA operative and then throws him out a second story window multiple times after the man harms Mrs. Hudson later in "Scandal".
Fakes his own death to protect Watson, Mrs. Hudson and Lestrade in "The Reichenbach Fall".
Note that he does the last one by jumping off of a building, likely using the same deductions he used to throw the CIA operative repeatedly out a window with non-lethal results on a larger scale. But he still fakes his death to save those he cares about by jumping off of a building, which still has the somewhat expected results of just nearly killing him instead.
Manipulative Bastard: Tricks victim's distraught family members into giving him information, lies his way into locked apartments, and so on.
Married to the Job: Celibacy aside, this is the reason he gives for why dating (or human social interaction in general) isn't "his area". You can count the number of people close to him in any sense on one hand.
Morality Pet: John, Mrs Hudson and Molly all serve to keep Sherlock grounded.
Motor Mouth: Whenever he goes into a Sherlock Scan. We're talking supersonic or even relativistic speeds here. It's entirely possible that Cumberbatch doesn't need to breathe; for example, just listen to his explanation of John's phone or much of "Hounds of Baskerville". And whenever IreneAdler is around he somehow manages to go even faster.
In one interview, Gatiss comments on the extreme length of the deduction in Baskerville; apparently, on Cumberbatch's script he actually wrote "Sorry, Benedict" next to it.
Must Have Nicotine: It's impossible to sustain a smoking habit in London nowadays, so Sherlock confines himself to patches. It just might end up being "a three-patch problem".
Goes absolutely haywire in "Hounds of Baskerville" when he's detoxing, turning the entire flat upside down and outright begging John to give him a cigarette.
Sherlock Scan: Demonstrated brilliantly. Even John admits to being impressed.
The Sociopath: Played with regularly. Sherlock has all the classic signs of a fictional sociopath: a general lack of empathy; self centered behavior; total disregard for laws; regular use of fake charm, lies and manipulation to achieve his goals; he even goes so far as to call himself one. Ultimately subverted however, since when push comes to shove Sherlock really does care about his friends.
The Spock: John even calls him "Spock" in "The Hounds of Baskerville".
Sticky Fingers: John's laptop, Lestrade's warrant card, an ashtray from Buckingham Palace, and Mycroft's clearance ID.
The Stoic: Shows little emotion most of the time, especially compared to those around him at crime scenes or during an investigation.
Not So Stoic: Whenever John is genuinely threatened or in danger. Strap a bunch of bombs to or point a gun at the good doctor's head, and Sherlock's cool mask will evaporate in two seconds flat.
Also two moments in "The Great Game": When the elderly blind woman begins to talk about the soft voice of the person who kidnapped her, Sherlock frantically warns her against it, knowing that the kidnapper will likely detonate the bomb he has strapped to her as punishment, which he does. Later on, when attempting to solve the riddle of how the painting was faked before the kidnapper blows up a child, he's clearly freaking out. Despite his supposed interest in puzzles over people, the prospect of these two lives being lost deeply disturbs him.
When Mrs. Hudson is taken hostage, he rescues her, has Watson take her downstairs... and then proceeds to beat the crap out of her attacker and toss him out the window.
Is visibly shaken after his "encounter" with the titular creature of ''The Hounds of Baskerville", and even admits his fear to John.
Adorkable: Doctor Watson. Martin Freeman's support of Woolly Hat Day.
Allergic to Routine: As much as he complains about Sherlock's behavior, there's nothing in theory to stop him simply walking away - except, as Mycroft points out, he's nearly as big a danger-junkie himself.
Aloof Big Brother: Is somewhat distant from his sister, Harry, because he doesn't like her drinking.
Badass: We know (from a blog comment by Bill Murray, the nurse) that he's the recipient of at least one medal, and Sherlock refers to him as a "war hero" during the taxi drive to Brixton.
Badass Adorable: Whether it's shooting a guy dead under improbable odds, sassing back criminal masterminds who've kidnapped him or ordering around CIA agents who have a gun to the back of his head, chances are he'll be doing it in a cardigan. Also is strongly implied to be one of those people who start celebrating Christmas in October.
Blood Knight: John isn't traumatized by combat so much as he misses it.
Boring Yet Practical: Prefers to use diaries and cameras to record data instead of bizarre memory techniques. Also prefers to call the police using a phone instead of a gun, and would like Mycroft to call him instead of kidnap him.
"You know ... I've got a phone. I mean, very clever and all that. But you could just phone me. On m' phone."
Magnetic Hero: For someone who doesn’t go out of their way to make friends, people seem to quickly take a liking to him. At any rate, he’s a far more likable hero than Sherlock.
Morality Pet: For Sherlock, letting him know whenever he's said or done something "not good".
Mysterious Middle Initial: In "A Scandal in Belgravia", John H. Watson finally reveals his much-speculated upon middle name: Hamish.
Which of course lines up with Conan Doyle's canon. For even more speculation, see the pre-season-two debate on DI Lestrade's first name. Conan Doyle only gave an initial (G) which BBC expanded to Greg.
Nerves of Steel: You'd be amazed by how much he goes through completely terrified and yet keeps his calm no matter what. It's telling that the only time we really see him panic is when Sherlock drugs him with a chemical specifically designed to cause irrational levels of fear, and even then he keeps his head enough to get to the safest place possible and continually report what's going on.
There's a Freeze-Frame Bonus in The Blind Banker where you can see his resume, which says he's a trauma surgeon. That makes him combat trauma surgeon and people don't get that job without Nerves of Steel on several levels.
Nothing Exciting Ever Happens Here: A variant; John says "Nothing ever happens to me" to his psychologist's suggestion that he blogs everything that happens to him. And then a couple of scenes later, he meets Sherlock…
Throwing Off the Disability: His limp is psychosomatic, meaning that he can lose it when he forgets about it. In fact, he was actually shot in the shoulder, meaning that his leg is completely fine.
Vitriolic Best Buds: Him and Sherlock. Hardly a moment passes when they aren’t snarking at each other.
Undying Loyalty: Basically spits defiance when Mycroft asks him to spy on his brother on his behalf, something that he knows could end very badly for him. This is after he's known the man for 24 hours and has gone to one crime scene with him.
Unfazed Everyman: From who else but himself? He adjusts remarkably quickly to the weirdness that comes with being Sherlock Holmes's sidekick.
John: We've only just met.
Mycroft: And since yesterday you've moved in with him and now you're solving crimes together. Might we expect a happy announcement by the end of the week?
What the Hell, Hero?: If Sherlock's getting one of these, chances are good that John will be the one lecturing him, and chances are that he'll be the only one Sherlock will even try to listen to.
With Friends Like These...: With Sherlock and cranked Up to Eleven in "The Hounds of Baskerville" when Sherlock drugs John and then locks him up in a lab to conduct an experiment that involved scaring the crap out of John, a war veteran who still suffers from nightmares and flashback related to the battlefield. It's surprising that John didn’t at least take a swing at him afterwards.
Wouldn't Hit a Girl: Violence against women seems to bother John. He is notably guilty about Soo Lin's death in "The Blind Banker", becomes noticeably distressed at the crying woman in "The Great Game", and while he had no problem punching the Superintendent of Scotland Yard for calling Sherlock a "weirdo", he ignores Sally Donovan rubbing it in that Sherlock was not to be trusted.
The Bad Guy Wins: Sure, he's forced to commit suicide on top of a building and sure, his ultimate plan for killing Sherlock didn't work out in the end, but he still accomplished the first part of The Plan. Sherlock's reputation is ruined, and many suspect him to be a killer by the end.
Camp Straight: Keeps up his Camp persona after revealing his identity to Sherlock. Also delights in flirting with him, calling him "sexy" and "honey". As always, it's hard to tell what really motivates him.
Driven to Suicide: Zig-zaged. Looks suicidal when he realizes that in destroying Sherlock, he's actually won, and now has nobody who will pose a challenge to him anymore. Then changes his mind and says he'll manage. Unfortunately Sherlock then convinces him that as long as Sherlock has Jim alive, Sherlock can also stop Jim's plan. Moriarty promptly shoots himself in the head to make sure Sherlock can't beat him.
Evil Counterpart: To Sherlock. In this version, he lists his occupation as "Consulting Criminal", and his Insufferable Genius tendencies are played up just as much as Sherlock's. His goal, as it turns out, is to find a perfect counterpart — someone who is him. Sherlock indulges him, in the end, and admits as much.
Large Ham: His high-pitched voice and psychopathic mannerisms make him constantly appear on the edge of psychotic madness. He also changes his tone of voice and his mannerisms about every other line, rapidly going through affected personas and acting styles just to mock Sherlock. He's always hammy, though.
Thanatos Gambit: "The Reichenbach Fall". To ensure that there is no way for Sherlock to stop his plan, he kills himself, thus forcing Sherlock to commit suicide to protect his loved ones.. apparently all For the Evulz.
The Unfettered: Ultimately a deconstruction. Having absolutely no empathy and no limits, Jim's one and only concern is to try and stave off his endless boredom... even if that means putting his own plans and well-being at risk to do it. Best illustrated in the second series finale where Moriarty gleefully shoots himself in the head for no reason other than he thinks it's the best way to "win" his game with Sherlock.
Unwitting Pawn: Makes one out of Molly Hooper, Sally Donovan, and the entire British legal system and tabloid press in "The Reichenbach Fall". Such is his Manipulative Bastardy that he even makes pawns out of the Holmes brothers themselves.
Victory Is Boring: As Sherlock points out, there is nothing that Moriarty can't already steal or buy. No problem presents a challenge for him. And Jim absolutely can't stand it.
"Do you know the problem with a disguise, Mr Holmes? However hard you try, it's always a self-portrait."
Adaptational Badass: In the original stories, Irene Adler's impressive feat was simply seeing through Holmes' ruse and having the good sense to skip town while she has the chance. Here, she manages to con him into decoding top-secret, vital information which she then passes along to Moriarty, ruining Mycroft's day. It takes a last-second epiphany for Sherlock to recover himself and make up for his own royal screwup.
Big Bad Wannabe: For all of Irene’s cleverness, it’s still clear that she wouldn’t have gotten away with as much without Moriarty’s assistance.
Bitch in Sheep's Clothing: She may not have been a sweetheart when she was introduced but by the time the episode ends, it’s revealed that she’s complicit in terrorist plots and Moriarty's willing accomplice.
Bi the Way: She has been in relationships with both men and women prior to meeting Sherlock.
Brains and Bondage: A dominatrix who caters to the highest echelons of society. The only person to get several over on Sherlock Holmes.
Dramatic Irony: Spends most of "Scandal" trying to exploit Sherlock's "emotions" as well as his pride and in the end her own feelings for Sherlock turn out to be her undoing.
Easily Forgiven: She was perfectly willing to extort the British government for millions, enlist the skills of a psychopath, aid in a terrorist plot, and her manipulation and betrayal of Sherlock yet she still gets saved by Sherlock in the end and lives without any apparent consequences or moral development.
Fun with Subtitles: When Sherlock does his trademark scan, a subtitle floating beside the clue says what he's noticed. When he first meets Irene, all his scans get is "???????".
Jerk With A Heart Of Jerk: Let's be honest, whether she has feelings for Sherlock or not, it still doesn't stop her from treating him terribly or excuse her for working with Moriarty. She's made it pretty clear all through that episode that her self-interest comes before anything else.
Karma Houdini: For all the havoc and damage she caused, she still gets to survive in the end.
Laser-Guided Karma: She does everything she can to exploit Sherlock’s naivete when it comes to sex and intimacy but in the end her own feelings for him prove to be her downfall. Verges on Dramatic Irony.
Mata Hari: One of her many tricks for stealing blackmail material.
Single-Target Sexuality: Caters to both male and female clients, claims to self-identify as being gay, yet the only man (or indeed anyone) she actually shows any serious interest seems to be Sherlock. Her chosen password is particularly telling.
Woman Of Wealth And Taste: The phone everybody was fighting for in "A Scandal in Belgravia" was a Vertu Constellation Quest smart phone, with a price tag of £17,300. There was more than one reason she was fighting tooth and nail to get it back.
Distracted by the Sexy: Molly's Christmas dress in "Scandal" causes Lestrade to need to pick his jaw back up off the floor.
Donut Mess with a Cop: When Sally startles Lestrade in his office at the beginning of "Reichenbach", it's to find him with his feet up on his desk, classily stuffing his face with a doughnut and talking with his mouth full.
Hero of Another Story: Cast by Moffat and Gatiss specifically because Rupert Graves gave off this trope when he played the role.
Inspector Lestrade: Played with. He is, of course, Inspector Lestrade himself, and often acts as if he's only there so that Sherlock can tell someone "no, you're completely wrong," but most of the time he lends himself more to a Friend on the Force role.
Lawful Good: In-universe, while he briefly seems to contemplate that Sherlock might be a fraud, he shows up to speak to Sherlock first before returning with a warrant to arrest him. Even then, he warns Sherlock and John in advance, causing John to lampshade this.
Green-Eyed Monster: She appears more than a little resentful of Sherlocks abilities. Especially when the media start painting him a hero.
Jerkass: Towards Sherlock. Sally rationalises her antagonism towards him as a being a result of Sherlock enjoying his work a little too much. She's notably much more personable toward Watson, encouraging him to leave Sherlock as it'll likely end badly for him.
"Never mind that, we found the case! According to someone, the murderer has the case, and we found it in the hands of our favourite psychopath."
Bad Cop/Incompetent Cop: It's unclear if he's actually good at his job or not, since all we hear is Sherlock trashing him. In the original pilot, Lestrade seems to treat him better.
Implied that he's not completely incompetent, considering Sherlock asks for him specifically in "Reichenbach" (despite reluctance in "A Study in Pink", which he claimed was because "Anderson won't work with me").
Bullying a Dragon: Sherlock only has to sniff him to figure out he's having an affair with DS Donovan.
Butt Monkey: Sherlock can't stand him, and as such, treats him horribly.
"Anderson, don't talk out loud, you lower the IQ of the entire street."
Gratuitous German: Apparently knows enough to tell Lestrade and Sherlock that "Rache" is German for revenge.
With perfect pronunciation no less!
Lab Rat: An in-the-field version, as he's a crime scene tech.
Unwitting Pawn: He gave Sherlock's life story to Moriarty (who he knows is dangerously obsessed with his brother) in exchange for something that, it turns out, never existed in the first place. Whoops.
Secret Keeper: Her final scene with Sherlock in "The Reichenbach Fall" and Moriarty's failure to include her as among the people Sherlock cares about that he can threaten imply that she might be the only person who knows Sherlock isn't dead.
As You Know: Her screen-name is "Marie Turner" which is her friend's name (Mrs. Turner, next door, with "the married ones"). Becomes a Running Gag on Sherlock's site and John's blog where every time she comments, she immediately double-posts a reminder: "It's Mrs. Hudson, by the way."
With the exception of the one time Mrs Turner herself actually commented.
Berserk Button: Harming her is officially Sherlock's, considering he throws her attacker out a window multiple times.
Being rude to her is another, even stunning Mycroft with how angry he got when Mycroft told her to shut up in irritation.
Don't lead her on, or let her find out about your marriage from Sherlock.
Catch Phrase: "I'm your landlady, dear, not your housekeeper!"
Cloud Cuckoolander: She's cheerfully oblivious to most of Sherlock's strange living habits. Or she simply doesn't care. That said, she does have a bone to pick with a few of his habits. Upon finding that Sherlock keeps thumbs in the fridge, she reacts with disgust, and she also seems extremely panicked by him shooting holes in the wall- though her reaction to this is just to scold him like a child and add repair costs to his rent.
Mrs. Hudson: I'm putting this on your rent, young man!
Cool Old Lady: Mrs. Hudson is one of a select few who can tolerate Sherlock for extended periods of time, gave Sherlock a special deal on the apartment (as thanks for helping her out with getting her husband executed), and keeps some kind of "herbal soother" in her apartment that she doesn't want the cops to know about.
She also pretends to be much more of a fragile old woman than she actually is when captured by the Americans in order to hide the fact that she has the phone they're looking for. When Sherlock throws the guy out the window, her first reaction is simply that her bins are getting dented.
G-Rated Drug: Her "herbal soothers" she doesn't want the drugs bust to find.
Informed Deformity: Her notorious hip has come up multiple times, and yet, she's never seen limping or otherwise uncomfortable because of it, and she seems to have no trouble going up and down the stairs in 221B.
Never Mess with Granny: Played CIA agents, police officers, and even Watson himself in "Scandal" by faking tears and sneaking Irene's phone out in her bra.
Shipper on Deck: She initially assumes that John and Sherlock are a couple, and wouldn't be persuaded otherwise. However, after Season One (especially during the events of "A Scandal in Belgravia") it appears that she doesn't think of them in that way anymore. Or perhaps she's just keeping that to herself now.
Sarah Sawyer (Zoe Telford)
Action Girl: Took on Chinese gangsters with a wooden stick.
Shadow Archetype: To Molly. Molly is a Dogged Nice Girl, Kitty is a Stalker with a Crush. And both of them prove to be rather important in "The Reichenbach Fall", as Moriarty sold his "story" to Kitty after Sherlock tore her down, helping to spread the belief that Sherlock is a fraud. Molly, meanwhile, despite being treated badly by Sherlock, still seems to step up to help him behind the scenes of "Reichenbach". Also, they both display admirable loyalty to Sherlock and Moriarty, respectively.
Slimeball: A rare female example. She reeks of desperation and uses every tactic in the book to wring a story out of Sherlock. It doesn't work, as he finds her repellent.
Too Dumb to Live: She's utterly convinced that Sherlock is behind several serious crimes including murders, but that he won't silence a witness if there's another easily-dispatched witness present.
Wrong Genre Savvy: Clearly thinks she's an Intrepid Reporter who has uncovered the truth that Sherlock is a fraud and responsible for the crimes he's solved, while Moriarty is merely an actor suffering a crisis of conscience. Alas, no.