The comic book. As Jim Butcher himself points out, The Dresden Files has the heart and soul of a comic book anyway.
The roleplaying game is both incredibly faithful to the books, condensing the Dresdenverse into a very elegant and functional game, and flexible enough to handle anything you might want to do with the game. An example is how a couple of people in one playtest group wanted to play as a ghost and a ghoul. They managed to figure out how to do so after about 10 min of planning for each.
One of the other playtester groups succeeded in making a character who was essentially an animated sentient whip.
Alternate Character Interpretation: After information revealed in Blood Rites and Changes, there's some debate about why Ebenezar didn't raise Harry from the beginning. Was it because It's Not You, It's My Enemies as the Blackstaff, there's probably no shortage of supernatural nasties who'd love to get their claws on a hostage, or was it because he was estranged from Maggie and literally didn't know Malcolm had died?
Awesome Ego: Ramirez. The Tabletop Game says as much. He has a habit of making jokes about his prowess in everything and he exaggerates it to the point of ridiculousness and is often Played for Laughs and in complete good humor more than once. However, when push comes to shove Carlos has proven to be extremely badass in not only combat and more than a little worthy of the jokes he makes. Except when it comes to his prowess with the ladies.
In universe, Gard blasting Ride of the Valkyries while saving Harry and friends in her choppers is noted by Harry to be particularly fitting. Also tells you something about Gard's sense of humor considering what the short story "Heorot" reveals about her true nature.
And in Cold Days: "We will, we will, rock you!"
Also in Cold Days, the orchestral version of .45 by Shinedown as Mab and Harry waltz over the remains of their enemies.
Awesomeness Withdrawal: After Ghost Story, the books have been taking increasingly longer gaps between publication. Fans would grumble about the usual year-and-a-half waits, but wouldn't complain too much. However, after Cold Days, it's taken two-and-a-half years between Cold Days and Skin Game, and ever since Peace Talks has been sitting in development five years counting, largely due to life hitting Jim all at once. Two books in the span of five years is starting to turn fans off from the series, though the occasional short story helps. As of March 2019, however, he is back to regularly writing and posting updates every few days as he finishes chapters.
Waldo Butters. On the one hand, he has plenty of fans of his slow, multi-book move from Zero To Hero, as an ordinary person still capable of great heroism and a refusal to be victimized. On the other hand, being the geeky schlub who gets a lot of nice things, including but not limited to the hot younger werewolf girlfriend, the magic skateboard, and the lightsaber, many see him as getting all of the things that the proverbial GM's little brother would find "cool".
Murphy. On one hand, she's a long-standing main character who's been in the series since the beginning and offers a vanilla human perspective, a staunch ally, and grounding for Harry. On the other, she's no longer Harry's contact with the police and no longer a potential candidate for Fidelacchius and, according to Word of God, will not have a power up like other characters, making people question her place in the series. Depending on whether people support Harry/Murphy or not, this has further split the base. This has gotten to the point topics involving Murphy on the official Jim Butcher forums regularly incite flame wars and locked threads.
Crazy Awesome: In Ghost Story, Harry was able to manifest his disembodied spirit into the real world and punch a mook, specifically because he was insane, which is the very definition of this trope. Recall that only insane ghostly spirits can manifest physically, because it's incredibly dangerous. Oh, and the way he comes to realize he's crazy enough to do this? He remembers all the other crazy stuff he's done in previous books. And much of that crazy stuff was awesome.
Ferrovax is an endless source of speculation and fan theories. He appears in Grave Peril for about 3 pages, with less than a dozen lines. But that's probably why. Being badass enough to have one of the absolute highest tiers in the series, canonically even stronger than the Queens certainly doesn't hurt.
Maggiemelted the hearts of readers in her first proper appearance in Skin Game. She's cute and clever from what we see of her, and pals around with Mouse.
Evil Is Sexy: Lara Raith is pretty much the embodiment of this, as are all the other Raiths, and both Fairy Courts, and Bianca and many of the Red Court vampires (before seeing their true form at least). Harry even mentions the benefits of having no hot water as taking cold showers constantly is a good defense against the supernatural charms of the dangerous female beings he meets constantly.
The Goodship Molly Dresden has a substantial fan following as well. Interestingly, this usually isn't against the Harry/Karren ship at all. More that in the long-term, supporters of the ship believe he'll move on eventually, given Molly's long lifespan.
Foe Yay: Harry and Lara have plenty of these whenever they meet or team up.
"Funny Aneurysm" Moment: The short story "Day Off", found in the anthology Blood Lite, features the characters of Kirby and Andi, the fact that they are going steady, and the fact that Harry is in a relationship with Warden Captain Luccio. In the book Turn Coat, Kirby dies and Harry and Luccio are told that their relationship was psychically arranged by the same Council traitor who killed LaFortier and Morgan. Consider the difference in tone between the two stories and you have got Mood Whiplash as well.
Genius Bonus: In Turn Coat it's stated that older wizards have greater resistance to mind-manipulation than younger ones. Older brains have less neuroplasticity than younger ones and are less able to form new neural pathways, which is what makes older people less mentally flexible than younger ones.
The first two books are okay, but the series really hits its stride at Grave Peril. It improves even more during and after Dead Beat.
Butcher really hit his stride when he had Harry punch a werewolf through a goddamn wall. After that the series figured out its pattern of stringing together incredibly awesome scenes with interesting mysteries and witty dialogue.
Really, the first three books focus heavily on Harry's job as a wizard-for-hire that frequently works with the police. Starting with Book Four, Summer Knight, the supernatural side of Harry's world takes over. Whereas before the focus was helping the cops with supernatural cases, as well as taking private cases himself that seemed to intertwine with the case the police were working, the focus now was on the many, varied worlds of the supernatural that Harry is involved in; the vampire world, the Fey world, the White Council, etc. Roots of this showed up in Book Three, Grave Peril, but by the time Summer Knight is over, the series is no longer about a wizard PI who works with the police, which was the initial premise.
Butcher himself lampshaded this when he made a statement to the effect that one of his regrets about the Dresden series is that people have to start it by reading the books he wrote when young and inexperienced.
James Marsters' in the audiobooks. For the first few novels, he lacked confidence, the track contains many slightly awkward pauses and mutters, and a few names and voices weren't nailed down yet. Compare that to James Marsters in Changes, where he's confident both in his reading and character impressions, Harry is the most emotional and raw-sounding than he's ever been, and he sounds genuinely invested; reads the text with utter conviction and sincerity, as much as any hardcore fan.
From "Changes". "If that was the price I had to pay to make my daughter safe, so be it. If I was haunted by my choices for the rest of my life because Maggie needed me to make hard choices, so be it." This passage is from when he was deciding to kill Lloyd Slate and become the Winter Knight. Applied to what happened later, when he killed Susan, there is a whole new dimension of haunting regret.
Another one occurs in Grave Peril, when Harry is waiting for Susan to bail him out of jail and sees Michael and Charity talking he finds himself wondering why all his relationships don't work and jokingly puts it down to all the "ghosts, demons and Human Sacrifice." cue Changes...
In the short story "Something Borrowed", Kirby was supposed to be Billy's best man at his wedding, but got really hurt in a fight the night before (no thanks to the jello shots)... Flash forward to Turn Coat...
In Death Masks, when Harry tracks Marcone to Persephone's bedside, he assumes the comatose girl must be Marcone's own child. He tries to keep up his hatred for the gang boss because of his many crimes, but a part of Harry can't help but think he might have become every bit as unscrupulously-ruthless himself, if he'd had a daughter who was helpless and needed him to fight for her. Several books later, Changes comes along...
When Molly began her apprenticeship with Harry, he stressed that she should avoid sexual relationships while training due to the possible effect it'd have with her powers. Come Cold Case, despite being out of her apprenticeship, Molly Can't Have Sex, Ever thanks to the Mantle's need to protect her maidenhood and, by extension, its power. Should she try and be intimate with someone, the Mantle will cause them severe injury.
Hilarious in Hindsight: In Backup, Thomas says that Harry and e-mails go together like Robert Downey Jr. and sobriety. Turns out, RDJ is AWESOME sober.
In Ghost Story, Skaldi Skjeldson asks Butters when he's going to get in the ring and "train like a man." Butters' answer is "About five minutes after I get a functional lightsaber." Fast forward about two and a half books, to Skin Game, and Butters takes up Fidelacchius, which reforges into something very recognizable. And when Harry points out to Butters how dangerous it is to be a Knight of the Cross, Butters replies that he has been talking to Michael about "training like a man."
Jerkass Woobie: When you read between the lines, you realize just how much shit Morgan's life has put him through. Four years on the Western Front in World War I is probably the least of his traumas.
Love to Hate: Nicodemus may be a genocidal, sadistic, despicable monster, but damn is his awfulness entertaining.
Gentleman Johnnie Marcone is constantly putting himself in a position where it's absolutely necessary for people who hate him to cooperate with him, whether because he's the lesser of several evils or simply the only option. Even before getting involved with the supernatural, Marcone brought all of Chicago's organized crime under his control. Upon getting involved in the supernatural, Marcone never fails to come out on top, repeatedly outmaneuvering and helping to defeat forces far more powerful and older than he is. Marcone even becomes the first mortal signatory to the supernatural Accords. Fully aware of his limitations as a man, Marcone is insanely prepared for supernatural threats and takes measures accordingly, frequently destroying threats that come for him. Marcone is also driven by a desire to protect innocent bystanders from harm, his iron will defined by a little girl who was once shot by a bullet intended for him. A complex, ruthless man, Marcone frequently shows why he is one of Harry Dresden's great allies and enemies often at the same time.
The White Court vampire Lara Raith, having been sexually enslaved by her own father, the White King, overcomes his control and cripples him into an empty shell that she uses as a puppet while she remains the true power behind the throne. Lara then proceeds to manipulate the rival families of the White Court into attacking female magic users too weak for the White Council to notice, betting on the fact that Harry Dresden will get involved and wipe out all of the challengers for leadership of the White Court. Lara is a consummate manipulator, frequently employing the aid of people who have reason to detest her and getting them to work towards her purposes. Lara is also secretly a fighter in the Oblivion War, seeking to exterminate ancient beings far too deadly to coexist with humanity. Despite freely acknowledging herself as a monster, Lara has a conscience, even if she will happily play her family, friends, allies and enemies to secure her goals and remain in power.
Martin, a seemingly innocuous member of the Fellowship of St. Giles, is a former spy for the Red Court in the resistance against them. Seeing all the horror and evil committed by his former masters shattered Martin's loyalty, making him a triple agent out to destroy them whatever the cost. Sabotaging a duel between Duke Paolo Ortega and Harry Dresden to keep a war between the Red Court and the White Council of Wizards ongoing, Martin later leaks information of his comrade Susan's daughter with Harry for the plans of Paolo's widow Arianna Ortega, letting her set up a sacrifice to wipe out an entire bloodline with its youngest member. Martin then manipulates a betrayal of the heroes to trick Susan into killing him, turning her into a full vampire so Harry is forced to sacrifice her, the youngest Red Court member, to exterminate the entire bloodline in order to save his daughter, dying with full satisfaction at his plans achieved.
Ferrovax. He's only shown up at the party in Grave Peril, and did comparatively little there. He's also one of the most popular characters among fans. Comparatively little being flattening a man with the tone of his voice.
Sue, the Tyrannosaurus Rex that Harry revives in Dead Beat.
Lasciel's shadow can make illusions so perfect that Harry can not tell the difference. She completely makes up a person to interact with him, and he is so taken in that other people start thinking he has gone nuts because he is talking to empty air. Then she demonstrates that if she wanted, she could use this to kill him at any time. Yeeeesh.
Also: The only purpose of a shadow when it's not being used as an avatar for the much more alien being in its coin is to get its host to pick up the coin again. You have to be, not only alive, but healthy and powerful enough to kill off anyone else who has also touched it, also has a shadow in their head, and will also be going for the coin. This implies that Lash's HeelFace Turn, while genuine from her perspective, is actually her programming creating another kind of trap for the host, by making him trust her when she's actually still fulfilling the purpose of the shadow. Even sacrificing herself is in service of that purpose, you can hardly pick the coin up if you're brain-dead.
He Who Walks Behind is an Eldritch Abomination whose distinguishing characteristic is that when it manifests it is always behind you. Even if your back is against a wall, it's still behind you. And now it just has a handy solid surface to pick you up and strangle you against. With one of its tentacles around your neck. Which it didn't have in the reflection you saw of it.
Nicodemus' lover is Deidre... his daughter. Her mom, Tessa, is Really 700 Years Old, but looks in her teens. The latter is actually mentioned in Skin Game, with Deidre telling Harry that they've been together for 2,000 years, and are far beyond conventional relationship terms.
Stoic Woobie: At the end of Cold Days, Mab certainly counts. Her daughter Maeve, was possessed by Nemesis and threatening to destroy the world, was killed before her eyes, and by Maeve's actions her second daughter has become the Summer Lady, keeping her from Sarissa and destroying the relationship of BFFs they had previously. The only hint we get of her deeper turmoil is when she admits to Harry who asked if she didn't like her choice to have Maeve killed, "[she] was mortal once."
As of Turn Coat, Morgan, although this may be Too Badass To Live considering his Jerkassness
Cat Sith, introduced as an uber badass malk, he ends up possessed by Nemesis. Even if he survived his fight with Harry, Nemesis appears to have destroyed his mind and taken over him completely. Ironically this is noted as lessening Sith's badass-ness in the process.
Unfortunate Implications: The repeated sexualization of women, to some; Harry has a tendency to describe attractive women in extended detail whenever he meets them, going on page-long monologues in some cases. A common counterpoint to this is that the series possesses a number of non-sexualized women note (Meryl, Helen Beckett, Luccio's original body, Martha Liberty, Ancient Mai, Anna Ash and most of the Ordo Lebes, the Mothers, and more), most of the jaw-droppingly beautiful women are not human to begin with, and Harry's fixation is presented as a clear character flaw that gets him into trouble often. It's generally left up to the reader to decide which holds more weight.
Yes, Susan, do gatecrash a party hosted by a vampire. A party you most certainly weren't invited to, never mind your forged invitation. This cannot possibly go wrong.
Officer John Stallings in Grave Peril. He trusts Harry enough to steal a key piece of police evidence for him: the personal journal of an occultist serial killer, but simultaneously doesn't trust Harry enough to mention said serial killer also killed himself a couple days ago, even when Harry asks him point blank about it. Stallings could have saved everyone a ton of trouble if he hadn't lied about that.
Officer Grayson falls for Dresden's lie that the bloody clothes and robes in the backseat of Dresden's car are just Halloween props.
Whether the show is a good adaptation of the books.
Whether Book Bob is better than TV Bob.
Complete Monster: Caleb, from "Walls", is a former thief and killer who possesses the Hand of Glory. Corrupting those who use the Hand, Caleb makes them degrade morally while also rotting them from the inside to empower his spirit. Murdering a young woman who tries to contact Harry Dresden, Caleb later kills another member of the thief group using the Hand, and then one of the last members before trying to corrupt and kill the final one. Manifesting, Caleb reveals his intention to murder Harry and the last boy before going on a theft and murder spree to celebrate his revival.
Harry's hockey-stick staff. Most agree, even if grudgingly, that a man walking around with a hockey stick would be far less conspicuous than a man walking around with a six-foot staff that looks like something Gandalf might carry. Credit where credit is due; in the series, Harry is less overt about what he is than in the books. TV Harry doesn't mind if people think of him as one of those "psychic investigators" police sometimes employ. Book Harry straight out says he's a wizard.
Butcher himself says that changing Harry's ride from a Volkswagen Beetle to a Jeep works for reasons both practical (filming in a Beetle would seriously limit camera angles) and character (Jeeps were intended for function over aesthetics and meant to keep running even under the worst of conditions), something Harry would very much approve of.
Bob being a ghost, not a disembodied knowledge spirit, due to every Harry/Bob scene having to consist solely of one actor talking to an empty set while the other actor's lines were added later in ADR.
They Changed It, Now It Sucks!: The reaction of the bulk of the book fans when the show started. Reasons ranged from the reasonable (the series was far less "quirky" than the books and more a mainstream supernatural show) to the outright weird (Murphy is supposed to be blonde, dammit!)