These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
"Death Note? Man, I love that anime/movie. What, there was a manga?"
Individual scenes are subject to this as well, even amongst fans who know the manga. The infamous "potato chip" scene was understated and matter-of-fact in the manga, but bring up potato chips in reference to Death Note, and people either recall the over-the-top Japanese dialogue from the anime, or the even more ridiculous English dub of the same scene.
Notable examples of this are certain Narm-tastic moments such as L's reaction to the second Kira mentioning shinigami and Mikami's death. Just like in the potato chip example, the reactions of the characters were far more understated (and realistic) in the manga. And in the case of the latter, the actual death/suicide happens 10 days later and off-screen.
Misa Amane is way more accepted in Japan, Europe and South America than in North America. If she could see fan reaction to her, she'd probably wish the NA Death Note fandom was more like the Batman fandom; she'd be more popular then!
Anvilicious: The power to kill (without having to assume responsibility) is evil.
Ass Pull: Mello and Near also come almost out of the blue, in contrast to the usual pains the story takes to show the plans in action from start to finish.
Awesome Ego: Light Yagami the God of the New World. Also more subtly L-only the world's top three greatest detectives with his own L-screensaver.
Low Of Solipsism, which plays whenever Kira is on a killing spree, and Death Note, which plays to highlight a key point in the overarching conflict - the "I Am Justice" scene, for example - both qualify as well.
Basically, any of the epic classical music played. Leave it to Death Note to make writing in a notebook fucking EPIC. Or eating potato chips.
Coda ~ Death Note, the music played over the credits of the final episode. That scene really wouldn't have had the same power without it.
Die for Our Ship: Misa and Takada for getting in the way of L and Light. Takada gets this from Light/Misa shippers as well, some of whom actually cheered when Light killed her, even though he was only using both of them. To a lesser degree, Halle for getting in the way of Mello and Matt or Mello and Near.
Matt. He has very few panels in the manga, but is extremely popular in the fandom. To the point where you'd think he was one of the main characters.
Matsuda established himself squarely in this place when he pulled a Crouching Moron, Hidden Badass moment in emptying his revolver in Light when the later attempted to kill Near . Of course before hand he was one due to his carefree attitude.
Soichiro Yagami certainly qualifies. In most of the abridged series of the series he is made to be this supreme badass whom no one will question or talk back to.
Mikami is highly revered by fans for being arguably the most over the top user of the death note and for having a genuinely sympathetic back story. He's one of the few aspects of Part Two that's not a Base Breaker.
Beyond Birthday only appeared in the book spin off "The BB Murder Cases" and had a passing mention in the anime and manga, but became rather popular nevertheless.
Naomi Misora and Raye Penber for being intriguingly mysterious characters.
Between L's two successors, Mello gets a lot more praise as a character then Near for actually going out and doing his own thing whereas Near just came off as an L copycat to most of the fanbase.
Fanon Discontinuity: Many, many fans would like to forget that Rem kills L. Others like to ignore the bits involving Near and/or Mello. Some even take that a step further and pretend the second season as a whole never happened. And there is yet another group of fans who would very much like to believe that Light won and/or lived. And that's just the manga, there are those that much prefer how the movies went (though few would include L Change the World in their continuity).
Throughout the series, there a number of images that just happen to resemble crosses. And in the first opening credits sequence, Misora is seen holding the recently killed Raye Penber's body, looking uncannily like La Pieta art.
The first opening credits also shows a split-second image of Light laying on what appears to be a stained-glass window (in the second opening, this is repeated, only Light is shown more as a festering corpse).
Also in the opening credits is an image of Light handing Ryuk an apple, in what appears to be a crude mimicry of Michelangelo's ceiling painting of Adam and God (With Light as Adam, giving the apple more symbolism, and Ryuk as God, being flanked by Shinigami rather than cherubim). Also note how, in this image, Light has THAT chain handcuffed to his wrist, which leads off-screen. Is speculated to mean that the image may actually be larger, including L attached on the other end.
Iron Woobie: Soichiro Yagami. He's the most decent man in the series, but he has to suffer due to his son’s and L's actions. Punnotintended.
Jerkass Woobie: Depending on your view and how much sympathy do you retain for them, despite them doing many bad things, Light, Misa, Mikami, Mello, Beyond, and even Takada could qualify.
Late-Arrival Spoiler: The DVD covers spoil certain events of the series. Such as the one that has an image of dead L and Light gloating over him. Also if you take a peak at any fanfiction you'll know the ending to Another Note.
Magnificent Bastard: Light is practically the manga poster boy for this trope. L actually fits the requirements even better than Light. Mello might have become one with his final actions, if you choose to believe he had it all planned.
The second interpretation may not be that far off, given the creator stated "Lights life was ruined when he got the Death Note." Although this refers more to it being a corrupting influence then it being in control of him.
Misa Amane is a walking blob of Moe. Pigtails, Gothic Lolita, Zettai Ryouiki, squealing girly voice, all topped off with a Yandere personality. She's so Moe that she even Shinigami want to protect her. Also, Sayu.
Light and L have their moments too. Especially L, thanks to his personality quirks.
Light definitely falls into this trope. He did so many horrible things from killing Lind L. Tailor to killing FBI Agent Raye Penbar to killing Raye's fiancee, Naomi Misora, getting closer and closer for every bad thing he's done. While the ones listed above were to just simply stop them from getting in his way, he finally crosses it when he kills someone that wasn't getting on his way, was on his side, and ultimately loved him. He betrays and murders Kiyomi Takada, even after she did what Light told her to do, murder Mello. What makes it even worse is she is forced to burn herself to death and die slowly and painfully.
Don't forget Matt's epic scene of Noble Self-Sacrifice. 16 panels in the manga, less than 2 minutes of screentime in the anime, and yet his character is one of the most popular in the fandom.
Linda (the only female student seen at Wammy's house), has a fan following despite her minor role. She appears very briefly in the manga, and not at all in the original anime series.note However, she might make a very brief appearance Relight 2: L's Successors as the student who asks L what he fears; the character is unnamed, but this is a plausible bit of Fanon.
Pandering to the Base: The films change the ending so that L wins for no good reason other than to appease the hordes of Fan Dumb who wanted that to happen in the real story.
Though it also allows Soichiro to actually learn his son is Kira. Some fans considered his dying without ever knowing to be a copout.
Also counts as a Pragmatic Adaptation, as it eliminated the entire Near story arc and the need to introduce a cast-load of additional characters. The movie format doesn't lend itself well to adding the Time Skip and a new storyline from scratch.
Paranoia Fuel: Your life can be ended at anytime just by having some Japanese god write your name in a notebook. Moreover, it's implied that this happens all the time. And, the only fate that awaits you or anyone, for that matter is nonexistence.
Misa during the Yotsuba arc when she successfully outmaneuvers and controls Higuchi.
Also in the live action movies, where she's portrayed as a more sympathetic character, with the death of her family being shown as a constant source of pain for her, rather than just being forgotten about the minute she joins Light (who, in the movies, she comes to acknowledge as a monster who doesn't care for her, but she just can't quit him. Not to mention she has photos of her parents alongside her pictures of Light, openly says she should've died with Mom and Dad, and breaks down in tears when Light decides to kill his father.)
Ron the Death Eater: Soichiro Yagami and Misa regularly in L x Light Fan Fics. Also Rem for killing L. L-centric fics frequently derail Light. Light-centric fics often give L the same treatment.
Rooting for the Empire: Though it is who depending on which fandom you're asking. Both Light and L themselves are portrayed as no better than the other, with L being nominally good. Granted, Light might be a bad guy himself, but L is also equally popular for those who didn't agree with Kira's methods either. Those who agree with Mello being the successor of L rather than Near might count as this too.
Takada! Dear god Takada! Whenever fans talk about her, it's either that she was an informed intelligent fool who easily fell for Light's charms or a stuck up bitch, particularly on how she treated Misa. She even gets plenty of hate from fangirls who swore to exact their revenge on her for killing Mello.
Seasonal Rot: Apart from the final episode, the second part of the series, that is, everything after L's death, is almost universally considered to be inferior to the first. Whether this means "quite good, just not as good" or "so bad it never happened" depends on who you ask.
Take That, Audience!: Light's final defeat was deliberately made as devastating and pathetic as possible, complete with a speech ripping apart all his pretentions of being a hero through using the Death Note, in direct response to all the fans who saw him as a Draco in Leather Pants.
Tastes Like Diabetes: Misa's attitude gets like this at times, especially compared to the overall aesthetic of the series.
Too Cool to Live: This applies to pretty much all the characters that meet bad ends, but especially Naomi and Matt.
Naomi was actually an invoked case of this, as she was intended to last longer, but then Ohba realized she was so good at her job that it would strain suspension of disbelief too much that she hadn't caught Light within a few chapters.
The live action movies are also sexist. For example, Light and L are pointedly not chained together but Misa is chained up for the sake of comedy. Some other choices seem to be trying to address the sexism in the original story... and in doing so make it worse. 1) A token female is added to the taskforce—she receives no characterization and her sole purpose is to complain. 2) A subplot added in the second movie where Takada is being sexually abused by Demegawa has the unfortunate implication that "if you are being sexually abused in the work place you should just shut up about it." 3) There are two prominent female characters in the third movie-one is evil and the other is an idiot.
Misa in particular is treated as an inconvenience and as unimportant, despite being the driving force behind Light's rise to prominence. If she had not come to his aid, he never would have been able to do as many killings as he did without getting caught somehow.
Values Dissonance: Many western viewers take offense at what they perceive as Raye Penber's paternalistic and condescending attitude toward his fiancée, retired F.B.I. agent Naomi Misora — and, worse, her seemingly contented acceptance of it. (In the DVD Commentary, her English-dub voice actress Tabitha St. Germain said that that scene was particularly difficult for her.)
Viewer Gender Confusion: Mello, in the manga. Rem is female but looks androgynous. Also, Near who is male but is voiced by female VAs in both the original and the English dub.
Interestingly, Mello's original name was Near, and vice versa, but an editing error at Shonen Jump saw their names switched around.
Aizawa's "I hate Ryuuzaki and his way of doing things!"
Misa often spends her time whining about Light not loving her, and at the same time, acting like a womanchild who is still a bratty daughter of her deceased parents.
What an Idiot: Naomi Misora giving Light her real name. In the manga, Mikami gets noticed by the SPK when he is asking Kira for orders... on national TV. Also, Higuchi.
The police when L asks them how they would prove someone was Kira. Each one answers that they would somehow set Kira up so that he was videotaped using his powers. Apparently it takes a genius on the level of L and Light to think of simply tricking Kira into revealing hidden information about the case... even though that's a common police tactic in real life.