In the movie version of AKIRA, Kaori suddenly meets her end when a mutating Tetsuo accidentally pulls her in and she's crushed by his insides. Her death in the manga was more plot-relevant, as she's shot to death by Tetsuo's treacherous lieutenant and perishes in Tetsuo's arms.
In Ashita no Nadja, Miss Applefield, who gets a shelf dropped on her off-screen as she performs a Diving Save to protect one of the orphan kids. This serves no other in-story purpose than having her Orphanage of Love disbanded and giving Nadja yet another reason to angst.
And another one is how Jose gets hit by a carriage right after he and Carmen have resolved to separate but stay in friendly terms until they truly reach their dreams.
Played for Drama in Attack on Titan with the death of Marco. He's killed off-screen without anyone knowing how he died, without the slightest semblance of dignity or glory. This shocks Jean to his core, and his greatest fear becomes dying a non-heroic death and having his bones be thrown and burned in an anonymous pile just like Marco's were. This drives his Character Development, as he not only wants to make sure that his death, should it come, is warranted, but he also doesn't want to let down Marco's high opinion of him. It is later revealed how Marco died, and while it does have a bit more plot significance than it initially lets on, it still stands as an inglorious way to die.
Despite being a fairly central character and being connected to several plot threads, it's later mentioned that Ymir was killed offscreen for her Titan Power.
In the final episode of The Big O, a side-villain named Vera gets into a Megadeus bigger than any other in the series, and gives a big, dramatic speech about how she will unleash a curse upon the city. Then, a beam breaks off of the mysterious giant stage lights over the city and falls on them. It is not acknowledged by the characters who witnessed it. The show must go on.
This scene made about as much sense as anything else that happened in the course of that episode, which was either a Gecko Ending, a Gainax Ending or a bit of both depending who you ask.
Pillar gets his head blown off by a cyberpsycho just as he and Maine's crew were returning from a bar.
Julio foolishly runs into a booby-trapped room and triggers a trip mine that instantly turns him into ketchup. David briefly mentions his death while sharing his day with Lucy, but no other mention regarding his death is made thereafter.
Danganronpa 3: The End of Hope's Peak High School Side: Future has Ruruka go out in the most brutal way possible: lacerated, choked to death with her own candy, and left in a position that made it look like something sexual was being done to her as she got killed. And considering the cause of death was suicide, the way she died raised a lot of questions about what issues she had with herself. Unlike most Foundation deaths in the show, this is the only one the cast doesn't know happened. All the people who would have mourned her went first, and the ones who did remain don't even mention her when the game is over. Even fans that thought of her as a Base-Breaking Character thought that was overkill.
Vamdemon's deaths from Digimon Adventure and Digimon Adventure 02. To quote one Digimon forumer, each of his forms was increasingly easier to beat. First form? All the Perfects had to combine their powers to allow Angewomon to strike him down. Second form? Hit him in the crotch with a chunk of building. Third form? "I wanna be a teacher!" POOF! The next time he'll be planet sized and bristling with firepower, and Neemon will kill him by sneezing on him.
And let's not get started on the deaths of Arukenimon and Mummymon.
A bit of irony in 02's case: by Digimon Adventure tri., nearly all of the Chosen save for Hikari and Takeru are trounced in a fight with Imperialdramon at the start of Reunion. There has been no trace of Daisuke and the group in the movies since.
Fairy Tail, a series marked for its habit of teasing character deaths and then not following through, abruptly kills off every government head in one swoop at the start of the Tartarus arc. An explosion mid-meeting kills Lahar and all or the councilors save Org, who is the killed several pages later.
Although a major side-villain and somewhat expected to die at some time during the series run, Full Metal Panic!'s Seina quite literally does have one dropped on her. By her own brother. The Behemoth's activation causes the structural supports for the warehouse to collapse around the main cast during their escape, including the water-filled room Seina is hanging onto a rail in. But we don't get to see that right then. Instead we see her about to shoot Andrey Kalinin despite the fact he came back for her. We see the gun go off as a cliffhanger to episode 11. In episode 12, we see Kalinin alive and Seina mortally wounded. In a flashback we then see her hit by a large girder which caused the gun to go off. That was pretty darned random.
Leonard's death is quite anti-climactic. He's the major villain of the latter half of the entire series,so you'd expect an epic mecha battle between him and Sousuke. Wrong! Kalinin merely shoots him because he's not ending the world fast enough. No big deal.
Chapter 36 in Fuuka ends with the title character very suddenly being run over by a truck and killed. Turns out the title was actually referring to a different Fuuka.
Although Ginga: Nagareboshi Gin manages to make most of its deaths impressive in one way or another, the manga-only wolf arc manages to make some exceptions:
Suiga's death, being taken into a pool of lava by one of Gaia'sChild Soldiers, seems rather quick and unimpressive by the series' standards. Made all the worse by the fact that his comrades pay next to no attention to his death due to Akame getting tackled into the crater next... and surviving by using his ninja skills.
The Empire's eight warriors are supposed to be extremely dangerous fighters and they certainly show the ability to back this up. Later on, cue Raiga arriving to the scene and curbstompingat least three of themwith a single attack.
Gintama: After the long, arduous fights to protect the Shogun from all types of enemies, the Shogun ended up being poisoned at his own house.
Mobile Suit Gundam SEED Destiny has YunaRomaSeiran tricked into returning control of Orb to Cagalli when she reappears during Operation Fury when Orb is overwhelmed and on the back foot. Arrested for treason, they attempt to interrogate him to no avail. Yuna manages to escape from his captors when a Mobile Suit fight distracts them for a moment, but not seconds later, a GOUF Ignited is shot down in front of him and squashes him like a bug. If he'd just stayed put and kept complaining, he would have lived, but instead he's killed by the needless war he started.
In the epilogue of Battle Tendency, it's mentioned that Rudol von Stroheim was killed in action at the Battle of Stalingrad in World War II. The anime implies that he sacrificed himself to cover a retreat for his men, but a lot of people still found it a bit jarring that a guy who regularly survived injuries that should've been more than enough to kill a person throughout Part 2 (including being bisected), could be brought down by what were most likely ordinary soldiers.
Keicho Nijimura's death at the hands of Red Hot Chili Pepper is rather sudden and unexpected, given that there had been no prior build up to Red Hot Chili Pepper's existence.
Aya Tsuji is killed by Kira very shortly after the heroes find her after she was forced to help Kira escape.
Leone Abbacchio is killed by the boss of Passione after being left completely defenseless. It's so sudden that Abbacchio himself doesn't even realize he's being attacked until afterDiavoloputs a hole through his stomach.
In what's perhaps the most notable example of this trope in the series, Narancia Ghirga, without any warning, is killed by Diavolo... off-screen. No Heroic Sacrifice, no last-ditch effort that helped the Bodyguard Team beat Diavolo... he's just stuck through a wrought-iron portcullis.
In Stone Ocean, after realizing there's another agent of Pucci around, Anasui suddenly kills Guccio by having his Stand, Diver Down, expel Guccio's ribs from his chest.
Hot Pants becomes a victim of Valentine's D4C: Love Train. Her death happens so suddenly in the already very hectic climax to the Part that many readers may not even notice she died until it's explicitly mentioned.
JoJolion: After being built up as a possible Big Bad for a large part of the series and the huge implications this would have on his family, Jobin Higashikata is suddenly handed an unceremonious death by hair spray can from Wonder of U. Like with Hot Pants above, his death was so sudden that most didn't know he was actually dead until it was confirmed later.
In Joker Game, two characters gain prominence in the first two episodes: Lt. Sakuma and a particularly clever and adept-seeming spy, Miyoshi, who appears to be on the way to becoming the former's foil. However, Sakuma vanishes from the story after that, the series reveals itself to be episodic, and the next time Miyoshi is shown, he's been killed while on a mission and doesn't even have any lines in his own focus episode. He's the only D Agency spy to die during the course of the series.
The Legendary Hero Is Dead! starts out in this manner, with the legendary hero dying by falling into a very obvious spiked pit trap (complete with a chunk of pork as bait). Then the villagers bury the body in an unmarked grave and pretend he was never there, just to avoid further trouble. Later, the protagonist (the guy who set up the trap to begin with) plans to defeat the demon lord in the exact same way.
The title character in Magical Princess Minky Momo suddenly lost her powers after her magical pendant was destroyed by an ordinary bullet and was run over by a truck out of nowhere shortly after. The creators of the anime did this in retaliation to the toy company that sponsored it pulling out due to poor international sales. Though she got better later.
Magical × Miracle has the Master Wizard, Sylth, who died after getting hit by a carriage. Quite an anticlimatic end for someone known to be so powerful.
Martian Successor Nadesico: Gai Daigouji (real name Jiro Yamada), suffers this when he's unceremoniously shot by Admiral Munetake while he and his cronies are escaping from the Nadesico. This after he'd been making a huge deal about how a man should die sacrificing himself for his comrades, and his death continues to affect Akito for the remainder of the series.
Orochimaru gets shafted twice. First, he is killed in a relatively brief fight with Sasuke, when his own body transfer technique is turned against him and ends up getting absorbed by Sasuke. Later, while fighting Itachi, Sasuke's chakra gets drained causing Orochimaru to be "freed" only for Itachi to seal him in a permanent genjutsu before he could do anything. Subverted because he comes back later.
Dosu challenged Gaara between stages of the Chuunin exam, and got killed instantly for his troubles because Shukaku was in control of Gaara's mind.
Directly afterward, a second bridge is dropped on the Chunin proctor, Hayate Gekko, who saw it happened, heard Kabuto and Baki talking about the invasion, and was killed off by Baki right there with almost no build up. His girlfriend in the ANBU ops was among those who found the body. She swears revenge on his killer and is promptly Brother Chucked.
In the final arc, this happens to none other than Uchiha Madara. He has successfully absorbed everyone except the main characters into the Infinite Tsukuyomi illusion and even the main characters trying to stop him are on the ropes. When it appears that he is a couple of steps away from victory, he gets backstabbed (literally and figuratively) by The Dragon Black Zetsu.
Negima! Magister Negi Magi: In the Gecko Ending of the first anime series, Negi's father Nagi, the legendary "Thousand Master", for whom Negi has been searching the entire series (and most of his life), is casually disposed of by shoving him through a dimensional portal so that Negi can get to the real business of the show's Grand Finale, which is retconning the bridge dropping of another character.
In the world of One Piece, where people seem to be able to survive about anything (including gunshots, explosions to the face, losing thrice the amount of blood a human body even contains, getting building thrown onto them, being poisoned to death, getting impaled, getting eletrocuted by millions of volts), Zoro's Childhood Friend Kuina dies an extremely anti-climatic death. While all other Straw Hats usually have a tragic backstory with a person in their past heroically sacrificing themselves, or dying an epic death, Kuina dies by falling down some stairs.
Deliberately used as the climax of the Wham Episode in Puella Magi Madoka Magica, when Mami Tomoe gets killed with shocking suddenness by the Witch Charlotte, who pulls a One-Winged Angel form out of nowhere. To be fair, she gets a slo-mo Oh, Crap! moment, but the whole scene is deliberately done with shocking suddenness, making this something of an Intended Audience Reaction.
Happens to Kyoko and Mami - yet again - in Homura's second timeline from episode 10. After realizing the truth about magical girls, a grief-stricken Mami snapped and shot Kyoko dead with zero warning whatsoever, then tried to kill Homura in the same fashion. She was shot dead by Madoka before managing to do so.
Offscreen, but in Fullmetal Alchemist (2003), Izumi dies somewhere between the end of the series and The Movie. Justified that she was quite sickly but still.
Word of God says this was originally not the case. Izumi had a completely written scene, her Tear Jerker death, but it was written out of the script. Her voice actress was even apologized to, for making her have no lines.
In the end of the first arc of Rave Master, Haru's father, Gale, dies shielding him with his own body from falling rocks. That would be heart-warming, if not for the fact that both Gale and Haru have always exhibited superhuman levels of strength and endurance, and also the traditional feats seen in Anime. A bridge was definitely dropped here.
In Sailor Moon the last three of the Witches 5 get very anti-climactic deaths. Each of them is killed within one episode - Tellu is destroyed by her own plant monster, Viluy is killed by her own nano-machines and Cyprine gets tricked into killing herself. In contrast Eudial and Mimette got long-running arcs leading up to their eventual deaths.
In Sailor Moon Crystal, the shitennou aren't killed one after the other and stay alive together long enough for the senshis to free them of their brainwashing...only to be killed in the next scene by an energy wave sent by the arc's big bad.
In Soul Eater, South American Death Scythe, Tezca Tlipoca seemingly dies this way. However he replaced himself at the last second. And he seems to have died again just seven chapters later. Although this time it seems to be for real, although it seems like way less of a bridge drop this time around since it not only got some fanfare, but the whole chapter devoted to the fight that ends this way. He's techincally still alive.
The manga version of Kimba the White Lion has Kitty who got killed off by a plague that came out of no where.
Wolf's Rain did something similar in the four OVA episodes that conclude the series. Remember, the wolves were trying to get to Paradise, and the series up to that point had suggested they had a chance of making it — so the first time one of the wolves died it was especially shocking.
Then again, the ending confirmed that they couldn't have reached Paradise anyway because it doesn't exist — the world is trapped in an endless cycle of death and rebirth and it's the wolves' fate to initiate every rebirth.
Happens in Xam'd: Lost Memories with Rival Turned Evil Furuichi. He's had his big fight with Akiyuki and Haru, his childhood friends and two of the show's heroes, and now it looks like he's finally made his peace with their being together and going to mend fences with them—only for the soldiers to catch up to him and arrest him for being a Xam'd, at which point he succumbs so deeply to despair that he tears off his own head! What makes this all the worse is that Furuichi is one of only a small handful of characters in Xam'd to die at all, and none of his former friends seem to care that he's gone—in fact, we never even see his mother's reaction to his death.
Zoids features a number of these, possibly the most infamous in episode 13 of Zoids: Fuzors. The climactic, three-way battle between the Liger Zero Phoenix, the Buster Fury and the Matrix Dragon (the latter which had been hyped as one of the most powerful Zoids ever just an episode prior) ends with the Buster Fury and the Matrix Dragon getting shot in the back by the Energy Liger. As a final indignity, the Berserk Fury and the Buster Eagle are seen in the following episode looking better than they did after they'd been shot, but being declared as "damaged beyond repair, no good even for scrap." What? (Made even more inane when you remember this is a Merchandise-Driven series, and the sole reason Buster Fury is being written out is to be replaced by the Gairyuki.)
. If he'd just stayed put and kept complaining, he would have lived, but instead he's killed by the needless war he started.