The bug with Hakkar the Soulflayer's initial release in Zul'Gurub, where his Corrupted Blood debuff became a plague upon entire servers due to a programming error. This is an incredible simulation of what happens in a real epidemic, right down to the breakdown of travel, the desolation and devastation of major urban centers, the retreat of people into isolation, the collapse of large-scale trade, everything. The way it spread from a minor error with how the debuff's interaction with pets was handled is also an interesting parallel to the worries of influenza jumping species. It was how an epidemic plays out in real life, historically. For all intents and purposes, it was an epidemic. Such a small bug. Such a large body count.
There were shades of this with the plague zombie infestation before the release of Wrath of the Lich King. Players could get infected (via roaches, rats, and 'conspicuous crates') and then become zombies, and then fight other players and NPCs, thereby spreading the plague. This turned the capital cities into Zombie Apocalypse battlegrounds. Whether this was Awesome or Fail depends on your viewpoint: while it was fun being a zombie or fighting to stop them, when things were at their worst it was very difficult to do anything in a capital city (where the auction houses and most banks and class trainers are located).
Most of the division is based around what some people did when infected. There were those that would play it out like an actual zombie apocalypse and try to infect as many areas of the world as possible. From lowly Crossroads and Goldshire all the way to the capital cities. They did it for fun and immersion. Then came the people who did it as a method to grief players, especially low levels. They would kill auctioneers, trainers and bankers making them unusable for stretches of time. Blizzard was pleased ultimately with how it went down regardless, and probably considered it acceptable as such. The purpose of the plague was to totally disrupt the tedium that nearly every player had fallen in since half way. Though it seemed to be those very people that objected most, seeing as they could not use the auction house to make gold or just hang around without worrying about paying repair money because someone infected them and they were killed by a guard.
What makes it awesome is that the incident has been studied by pathologists in an attempt to predict how a real epidemic would play out, and might end up saving thousands of lives.
The Balance of Light and Shadow for Priests. After looting the Eye of Divinity in Molten Core, you would head out to Eastern Plaguelands and meet an NPC priestess who tells you her story of how she failed to save Stratholme peasants as they fleed from Arthas and his Scourge and how the now-ghosts must relive the experience. She tells you that you must succeed where she failed by saving at least fifty out of sixty-five peasants as Scourge Archers attack them and lesser Scourge attack you. Other players may not interfere for a demon called The Cleaner will spawn, instantly kill them, and end the event. This event was actually pretty difficult in its time. The vast majority of Priests would fail in their first attempt. Most would find friends (or even a Priest of the opposite faction if he/she happened to be there) to exploit around The Cleaner and Priests would seek out full buffs from every other class and use consumables. Successful completion of the event yielded the Splinter of Nordrassil. When combined with the Eye of Divinity and the Eye of Shadow, the Priest receives Benediction, a staff that Priests at 60 would wear past Blackwing Lair and level 80 Priests still farm for because it's one of the best-looking staves in the game.
Of note is "Rewriting the Battle of Darrowshire." It required a small raid back in the day, plus the two commanders and their respective squads of militia. The enemies started off as weakly-made skeletons, but by the end you were facing squads of knife-wielding freaks known as The Bloodletters. Then of course, there was Horgus the Ravager, the mid-boss, and Mardek the Black, who fights you by proxy, forcing you to fight Redpath the Corrupted. Killing that bastard Mardek later in the Scholomance is an incredibly satisfying revenge.
Even better, soloing it (it's been nerfed now, but it was incredibly intense with a feral druid pre-Cata)
The Dreadsteed of Xoroth questchain for Warlocks was truly epic in classic WoW. Over the course of the adventure you mass murder creatures created by the moon goddess and collect their blood, infiltrate the Shadow Council, rip out an orc's heart, wreak havoc across two dungeons, fight off an army of demons as you prepare a portal, and kill a Dreadlord so you can steal his horse. Your reward? Quite possibly the coolest looking mount in the game ever made. Shame they took the questchain out in Cataclysm and you just buy the Dreadsteed now.
Part of the shame being that the only people who did it post "Burning Crusade" were people with a few bored friends, a lot of time, and a lot of gold on their hands. (Then again though, the gold wasn't hard to get) Around Burning Crusade, the game started handing more money per drops and quest rewards so it eventually became cheaper (and way more efficient!) to just purchase the same mount everyone else did.
The Summoning the Charger quest chain for Paladins. It involves exorcising an entire town, getting holy water from the heart of the Scourge in the Eastern Kingdoms a dungeon all in itself. Save a spirit from another dungeon. and after all that. Two diamonds, and the censer you used to exorcise the town are then put together. After that you actually invade the Scholomance, an entire school of necromancers to get a death knight's attention, kill him, and free the charger. Thats right, you steal a death knight's warhorse by raiding an school of necromancers and killing him in there. Your reward? A epic, glowly, heavily armored warhorse that literally came back from the dead.
Tirion Fordring appearing at the end of the quest In Dreams, in which he confronts Isillien, facing him and his elite bodyguards in combat and wins, bringing down the hammer of justice on his son's murderer.
The Burning Crusade
The Bash'ir Landing raid, which isn't an official quest, but forces you and your raid to defend a scientist while she examines some kind of device. It starts off with you fighting a wave of mooks and a Fleshbeast mid-boss, followed by another wave with three siege towers assaulting your position. In the end, your raid has a standoff with The Collector, an ethereal who can split himself into three and has some deadly lightning spells.
Wrath of the Lich King
Tirion Fordring gets a couple of these in this expansion.
Confronting Arthas at the Battle of Light's Hope Chapel and purifying the cursed sword Ashbringer by sheer force of will, then stabbing the immortal Lich King with a single leaping blow and forcing him to flee.
Also, the Argent Dawn was losing the battle until Tirion showed up, and he was able to turn the tide even though the forces of the Light were outnumbered 300 to 10000. Oh, and by the way, doesn't "300 vs. 10000" seem a little bit like aShout-Out?
Arguably his greatest crowning moment is where he confronts the Lich King up on the Frozen Throne. Admittedly, it is a little lame that he gets frozen at the beginning of the battle, leaving you and your raid group to fight, but when the Lich King decides to show his true power and deal 1,000,000 damage to every member of your party, wiping you all, Tirion clealy isn't going to take it. He epically prays to the Light and it sees fit to send down a bolt of utter pwnage, smiting the ice block. Tirion the leaps forward, and cuts straight through Frostmourne, pretty much ending the Lich King's reign. Talk about awesome.
The final battle with the Lich King at the Frozen Throne is just one long CMoA, period. Between the epic danger of the val'kyrs snatching players up and tossing them off the edge of the Citadel, the massive pools of blight, earthquake spells, getting sucked inside Frostmourne, it's insanely fun, challenging, and keeps you on the edge of your seat. Even the scripted phase at the end is incredible. After the above mentioned shattering of Frostmourne, the thousands of souls trapped inside it break free and stun the Lich King, allowing you to open a can of whoop ass to finish him. That alone could qualify as a CMoA by itself, not to mention a Tear Jerker, when you consider it's the ghost of Arthas' dead father that resurrects you when everything looks hopeless, and it's the souls of all the people murdered/enslaved by the Lich King that help you bring him to justice. A suitably epic end for one of the most memorable villains in the Warcraftverse.
It's certainly one for Putress himself. Yes, he's an evil, traitorous bastard, but he managed to truly boil the entire Forsaken philosophy, the sheer zealotry of their all-encompassing hate of the Lich King and the Scourge, down into about a minute of screen time.
Grand Apothecary Putress: Did you think we had forgotten? Did you think we had forgiven? Behold, now, the terrible vengeance of the Forsaken! Death to the Scourge! And death to the living! (the New Plague continues to do its thing in the armies below) Now, all can see this is the hour of the Forsaken.
Also Saurfang the Younger riding up triumphantly followed by the Horde and his call to his people.
Bolvar Fordragon's appearance and his charge into combat.
The player characters receive their own Crowning Moment of Awesome when performing the Storm Peaks quest chain, as the Drakkensryd event has you battling mounted drake-riders while several hundred feet in the air... by harpooning their drakes, leaping onto it alongside them, and throwing them off. Later on, you get a daily quest to tackle a flying dragon in midair, hang on and climb to its mouth, and then throw the Spear of Hodir down its throat, Odin-style. It's like Kratos dropped in for a visit.
Thorim, an ancient viking type being who is a major character in this chain, gets one for jumping off his throne, falling just under two kilometers, and landing on his old mount.
The Taunka Chieftain, Roanauk Icemist. The guy is in chains when you find him, not sobbing in despair, but getting angrier and angrier at the Crypt Lord who chained him up. When you free him, he demands that the Crypt Lord face him. The beetle refuses, so Roanauk jumps up a waterfall, grabs the Crypt Lord (Who is a tank-sized armored beetle), and throws him off the cliff, just so that the Crypt Lord is forced to face him. He then proceeds to beat the beetle to hell and back. And to top it all off, you get to crown him High Chieftain of the Taunka. Best quest ever.
High Overlord Saurfang became a memeticMemetic Badass during the War of the Shifting Sands, but to most he just stood around in Orgrimmar actually doing nothing. With Wrath, it seems that he's not just earning his reputation, but surpassing it.
"We will fight you with every fiber of our being- Until we are nothing more than dust and debris. We will fight until the end."
Though you don't see it, one of the Frost Dwarves tells you how the Frost Dwarves met their current king, Yorg Stormheart aka Muradin Bronzebeard. A group of dwarves, returning from an undescribed trek across Dragonblight, stumbled across a mountain dwarf (a type they'd never heard of before), who couldn't even remember his name, lost in the snow, so they decided to take him back home with them. On the way, they were attacked by a giant jormungar (Giant, acid-spitting worms), who swallowed one of the group before they could even react. They thought they were doomed, "...but behind him, a furious roar rumbled across the snow, and he turned to see the mountain dwarf growing in size, his skin taking on a stone-like texture, and his hands sizzling with lightning. The dwarf barreled forward with a sound like rolling thunder and hurled a shining metal hammer, lightning coursing over its surface, directly into the jormungar's throat. The jormungar collapsed instantly, its head barely still attached to its convulsing body." Do NOT mess with Yorg/Muradin
The intro cinematic for Wrath of the Lich King. Arthas waking from the Frozen Throne, stabbing Frostmourne into the ice which awakens Sindragosa, who then flies out over the armies of the Scourge, all of them roaring together. The epic soundtrack just adds to it.
The Death Knight's starting area has one where you mercilessly destroy armies of the Scarlet Crusade with a frost wyrm.
Zul'Drak has one quest chain where you free a storm giant named Gymer who's been captured and put in a cage by vargul. When you let him out you then ride on his shoulder and start trampling Scourge underfoot and taking out three of their commanders.
Similarly, in Sholazar Basin one of the quest chains the Avatar of Freya offers has you riding on the shoulder of an ancient golem known as The Etymidian and punching the shit out of Scourge on a mountain.
The Darkspear leader Vol'jin gets one in Cataclysm, as he opposes the other trolls who want to rebuild their ancient empire. Mixed with Heartwarming Moment.
Troll: You dare to stand against your people!? Vol'jin: The Horde is my people!!
Vol'jin gets another one during the Troll starting quests, where he shows you a vision him him telling off Garrosh.
"I know exactly what I'll be doin' about it, Son of Hellscream. I'll watch and wait as ya people slowly become aware of ya ineptitude. I'll laugh as dey grow to despise ya, as I do. And when that times comes, when ya failure is complete and ya power is meaningless, I will be there ta end your rule. Swiftly, and silently. You will spend ya reign glancin' over ya shoulder, and fearin' da shadows. For when the time comes, and ya blood be slowly drainin' out, you will know exactly who fired da arrow that pierced ya black heart."
And as of the Siege of Orgrimmar, it's true. The dark heart of Y'Shaarj, that is.
That doesn't even take into account how you reach the Maelstrom. The raid parachutes onto Deathwing's back where they must tear his scales off while his own immune system comes to life to stop you. Once his scales are gone, Thrall shoots him the Dragon Soul which shoots straight through Deathwing's chest and causes him to plunge into the Maelstrom.
The Battle for Gilneas quest for the Worgen starting area. The player must fight and drive the Forsaken out of his home, fighting alongside the leaders of the nation and a small army of Worgen and regular citizens. You felt the Gilnean pride when listening to Prince Liem's Rousing Speech before making the charge.
Mists of Pandaria
Alliance players start Mists by storming into Pandaria on the Skyfire, after which you jump onto an Gyrocopter and Unleash Hell, no, that's literallythe quest name rain down Gatling gun rounds and missiles onto the Horde.
The Jinyu quest line where you give out weapons to a bunch of Pearlfin acolytes and train them by fighting in the wilderness. Afterwards you and the 4 you trained go out into battle against an army of the newly Horde-aligned hozen, who vastly outnumber the Jinyu. You slaughter all of them, and kill their leader.For the glory of the Alliance!
The Hozen quest line the Horde get is pretty freaking awesome itself. While the Alliance get to recruit the Jinyu, the Horde have to work with the more short lived and dim-witted Hozen. The Horde ends up turning a chaotic band of idiots into an organized army that can fight against the Alliance's new forces! For the Horde!
The wall that keeps the Mantid out of Valley of the Four Winds is broken down by their Kunchong. The forces you gathered up questing there and in Krasarang Wilds come to save the day, but you save it most of all. You do this by letting yourself get eaten by the Colossus, and then utilizing special training you received from a pandaren martial arts master to punch your way out it from inside like a chestburster!
Just how amazing this scene is cannot be understated. The local commander of the Shado-Pan orders a retreat when the wall falls, but then Chen Stormstout himself arrives and kicks some Mantid ass. Following Chen are a group of four students who you had helped throughout Krasarang Wilds and the Valley of the Four Winds, and then Chen starts talking about how Pandaria belongs to them, their ancestors, and their children. Nearly every single named NPC you have interacted with, from the Crane acolytes to the Tauren and Night Elf settlers to the militia from Zhu's Watch to the humble farmers from the beginning of the zone, start running down the hillside ready to fight the swarm.See it for yourself!
On a smaller scale is the NPC Shomi, a MulanExpy in Kun-Lai Summit's Zouchin Village area. A young girl whose protective father wants her to be a lady. She's only just beginning to wonder if she'd make a better adventurer than Lady when the Zandalari attack Zouchin. Unable to just stand by, she asks you to teach her on a fight, resulting in a quest where you kill trolls with her at your side. After the quest, she returns to Zouchin, trains yet more defenders herself, and is a major defender when the Zandalari attack the village en masse.
The start of the Shieldwall/Dominance Offensive quests, where Varian Wrynn (for the Alliance)/Garrosh Hellscream (for the Horde) comes ashore, starts tossing orders around, and when he gets to the player, tells them that because they know the land so well they're to stick with him. Followed by one quest where you fight by the King's/Warchief's side.
The remixed Shieldwall/Dominance zone in general, It's basically The War Sequence, except permanent, on multiple fronts, with players on both sides. The Alliance going Normandy beach on the Horde base from The Skyfire? A full-out frontal assault on Lion's landing? Both happening at the same time? Yeah, all that and various secondary conflicts going on in just about everywhere else in the battlefield.
The climax of the Vale of Eternal Blossoms when you hit exalted is perhaps the coolest battle since the Death Knight starting zone, It starts with you checking on Zhi the Harmonious to find he's been killed, and the helm of the Thunder King has been taken from you, after fending off an ambush you return to Leven to find that the entirety of the Shao-tien army has arrived and is overwhelming the defenders. Leven sends you out expecting this to be the last stand, when a few kills in, the August Celestials arrive and empower you, from there, you tread into the vale at full power and proceed to single handedly destroy the entire Shao-tien army with almost zero effort. After this, you and Leven take the battle to the Mogu leader, Zhin the Bloodletter, the Smug Snake who's been rubbing your "inferiority" in your face during every main event in the quest series, and finish him off after a (Surprisingly difficult for this game) fight, you return to the Terrace where you get your dailies and are hailed as a hero by everyone in the vale.
A daily quest from the Klaxxi is easily this. The player rides a massive Kuchong (a smaller version of the Ik'thik Colossus above) and carves their way through enemy mantid. The goal? Kill 200 enemies and it's a breeze.
Patch 5.1 and Patch 5.2 increases the awesome moments for the Blood Elves of the Horde in general. When Jaina imprisons the Sunreavers from Dalaran due to Garrosh using Sunreaver spies to steal the Divine Bell from Darnassus using the Sunreaver's portal network, it's up to Rommath and the Horde heroes to break Aethas and the other non-imprisoned Sunreavers out of Dalaran. This includes freeing dragonhawks, executing a High Elf who feeds Sunreavers to Segacedi the Dalaran Sewer Shark, breaking Aethas out, and finally escaping from Dalaran from the sewers by jumping off of Dalaran! Lor'themar telling his forces to ready up in preparations for a battle is almighty enough, especially taking Rommath's praise that "he would make a suitable Warchief" in place of Garrosh himself.
Before that, you had the Purge of Dalaran itself, in which Jaina gets fed up with the Sunreavers and the horde in general betraying every agreement, just out and orders the sunreavers out of Dalaran, when Aethas refuses, she freezes him before he can even do anything and starts teleporting Blood Elves into the Purple Citadel while Vereesa orders you to stop the literal insurrection brewing in the sunreaver's quarter of Dalaran, which used to be a off-limits zone. You march in and singlehandedly slaughter the entire Sunreaver Garrison in there and then take down Sunreaver-aligned shopkeepers, who attack you on sight and a Sunreaver trying to loot the bank before running off. Following all of this, in 5.2 Jaina officially aligns the Kirin Tor back with the Alliance and takes the war to the Thunder King..
The climax of the main quest chain in 5.2 is a huge moment of awesome for Taran Zhu: After killing The Thunder King's second in command, a bleeding out and nearly dead Taran leaps into the middle of the Horde and Alliance forces and roars out the following quote, which makes both sides back down long enough to realize they're in agreement Garrosh has to go, and that they may still be closer allies than either side realizes. Furthermore, the exchange gets Jaina to finally realize she might have been wrong about the Sunreavers being complicit in the theft of the Divine Bell.
Taran Zhu yells: ENOUGH!! There will be no more bloodshed today. I see now why your Alliance and Horde cannot stop fighting. Every reprisal is itself an act of aggression, and every act of aggression triggers immediate reprisal. *Jaina and Lor'themar protest* SILENCE! YOU must break the cycle, It ends TODAY. Here. The cycle ends when you, Regent Lord, and you, Lady Proudmoore, turn from one another. And walk. Away.
5.3's Battle of Sen'jin Village features Chen Stormstout and Thrall helping the trolls fight off the invading Kor'kron. Standing at the gates to the village, Chen kicks approaching orcs into the air where Thrall proceeds to zap them with lightning until they explode.
Moira Bronzebeard taking the fight against the Frostmane trolls when her fellow dwarf leaders, Muradin and Falstad, are too worried about her stabbing them in the back for them to fight the trolls. The battle ends with Varian laughing that Falstad and Muradin will regret not being there to see Moira in action.
One for the Monk class in general. Touch of Death instantly kills any non-player character that has equal or less health than the monk. Cue level 90 monks one-shotting vanilla raid bosses.
Garrosh: Step aside Pandaren. You confront a force beyond reckoning. Taran Zhu: Your father dabbled in forces beyond reckoning. Where is he now?
Garrosh himself gets one for fighting Taran Zhu and winning. Especially the part where he punches Taran off the bridge.
It adds a layer of evil to him, but about as much badass. Garrosh isn't being controlled or corrupted by Y'Shaarj. He's doing this because he wants to. Even as the heart's power flows through him, it doesn't outright mutate or manipulate him, instead just forming over his upper half as a fleshy armor. He has successfully weaponized an Old God.
King Varian Wrynn: But know this: if your Horde fails to uphold honor as Garrosh did, we will end you.
And to be clear. This isn't just anything, Varian marched up his guards with him, making it very clear that this was the Horde's final warning, and any more aggression will not be tolerated.
Equally impressive was Vol'jin's response. Rather than react with bravado, or deliver taunts or oneliners, his response is to stand. To clarify, Vol'jin is such a tall and imposing figure he has to crouch constantly to even be at eye-level with Varian. And even then he's a few inches taller. After Varian more or less tells him "Behave, or we'll kill you" Vol'jin right there demonstrates how different he is from garrosh. He delivers no verbal threats, no bravado, or taunts. He simply stands to his full imposing height and delivers one hell of a Death Glare as to show this "high king" that the real horde is not going to be so easily crushed as garrosh's cronies were.
Another one is Thrall's "The Reason You Suck" Speech to the defeated Garrosh, a very effective and concise one that more or less the twelve exact words that hurt the most for Garrosh to hear them.
Thrall: You disappoint me, Garroshnote A call back to "Heart of War", in which Garrosh inwardly admits that Thrall saying that after their fight before the Scourge invasion got to him. You are not worthy of your father's legacy.
The short silent moment between Thrall and Varian is also great. When Vol'jin reveals himself, Varian was obviously expecting Thrall and looks over at him with a little bit of confusion. Thrall gives an absolutely perfect "deal with it" face in response.
You mistake your greatest strength for weakness. Do you not see this?
Warlords of Draenor
The intro cinematic for Warlords is pretty satisfying as an Evil vs. Evil fight between Grom and the Iron Horde and Mannoroth and Gul'dan.
To put it into context: Grom, when offered the Blood of Mannoroth, asks Gul'dan at Garrosh's prodding what price would the Orcs have to pay for the gift he was offering. When Gul'dan revealed his Fel Corruption and stated that the Orcs would have to give "everything", Grom deliberately spilled the Blood of Mannoroth on the ground, causing Mannoroth to personally show up to make an example of Grom; he is quickly interrupted by Garrosh unleashing the missiles of the Iron Horde upon Mannoroth, and calls in the Iron Star-chariot to chain Mannoroth down. Mannoroth escapes and launches a Fel infused Wave Motion Gun only for Grom to aim Garrosh's Iron Star at Mannoroth and fire it at him, causing an explosion which served as a smokescreen for Grom to embed his ax into Mannoroth's head. This not only killed Mannoroth, but also caused a similar explosion to the one caused by his death in Warcraft 3 (though this time Garrosh pushes Grom out of the way, saving him). After the explosion subsided, Garrosh approached Gul'dan, who pleaded that the death of Mannoroth was not the Orcs' destiny, only for Garrosh to say that "Times change." Pulling Gorehowl out of Mannoroth's corpse, Garrosh tosses it to Grom who promptly declares that the Orcs will never be slaves. He then declares that the Orcs will be conquerors.