10) Garrosh Hellscream
Despite being violently hated by a vast majority of both the Horde and the Alliance, Garrosh Hellscream remains alive and well at the end of the expansion. Despite seeming hell-bent on military confrontations that go through extreme and out the other side, such as blowing up random Alliance ships at the expense of his own air force, the Alliance counter-attack is meager at best. And, while three of the other four Horde leaders have solid, belieable, well-stated reasons for wanting him dead, he remains in charge of that faction as well. Finally, despite plenty of Horde players openly admitting their reluctance or refusal to defend him, his location in central Orgrimmar within stone's throw of the bank and AH makes him the best-defended faction leader in the game.
He can take comfort in the fact that he's now killed slightly less often than he was before. Before Cataclysm, this poor tauren punching bag could be felled by a soft summer breeze. Now, accidentally pulling this elite is almost a rite of passage, and Horde players routinely watch and cheer him on.
8) Illidan Stormrage
For being a central, if not THE central, figure in all of Burning Crusade, Illidan remained a baffling mystery to most players. Those who did not know their lore, but only played the game, knew him only as "You are not prepared". His backstory and history were not explained deeply in the game itself, and he was just some demon to fight. This was doubly true if, in LK or Cata, you plow your way through the 60-70 level range at warp speed. On the other hand, if you did study your lore, you wondered why he was the central figure in BC at all. After all, this is someone violently opposed to both the Burning Legion and the Scourge, both of whom are far more prevalent than Illidan's forces, as well as far more dangerous. He was, for all intents and purposes, trapped within the walls of the Black Temple.
Cataclysm finally has a decent answer to both. Illidan's appearance in the Well of Eternity gives this Warcraft main character the background he deserves, letting both new and veteran players know who this guy really is, and quite frankly, to feel a little bit better about roflstomping him in Black Temple. An achievement/guild achievement exists for wielding his paired blades, giving you yet another reason to go stomp him flat. He also drops the coolest-looking transmog shield in the game, I don't care what anyone else says. There are also rumors floating around at Blizzcon 2010 and 2011 that Illidan will make a further return.
7) Aska Mistrunner
7) The cooking trainer in Thunder Bluff
The release of the extra cooking dailies to additional cities points at something desperately needed in Blizzard's favor: that they are willing to spend time and resources into something as "minor" as cooking and fishing, and create a well-polished product. Thunder Bluff stands out amongst them, as anyone who actually reads the quest text knows, by offering the cooking quests that are the most appetizing. Especially when compared to, say, the Undercity. +2 to cooking skill for picking out top-quality ingredients is perhaps one of the most appropriate quest rewards in the game.
Vol'jin's victories in the Cataclysm expansion are twofold. Firstly, taking back the Echo Isles and making a brand new troll starting zone works out very well (yes I know the retaking itself was done in the LK expansion, shut up, make your own damn list). Secondly, he was without question the biggest figure in patch 4.1 for Horde and Alliance. No matter how you feel about "rehashed content", at least for a short while, it was all about da Vol'jin, mon.
The Bronze Dragonflight remains unique as a neutral faction as being important in every expansion in the game, especially Vanilla (you do remember opening the gates of AQ, don't you?) Nozdormu's individual appearance in the three final dungeons gives him a deeper, richer story personally than any of the other aspects, unless you happen to be on the staff quest. Also, he gets Chromie as an assistant, and that's pretty cool in and of itself.
4) Harrison Jones
In the Burning Crusade, Harrison Jones made his first appearance by wandering through the doors of ZUl'Aman and being one-shotted by the instance's first trash pack, which lived next to Wilfred Fizzlebang as the most embarrassing appearance in any raid. In Cataclysm, this death scene is entirely replaced by an extensive quest chain, spanning an entire zone, in which he is unquestionably more effective. This kind of drastic U-turn easily places him high on the list.
3) Sylvanas Windrunner
Sylvanas' appearance in the End Time could arguably be called the hardest encounter of the three new dungeons, as she fights with raid boss-style mechanics and frequently, yet justifiably, one-shots the idiots routinely found in LFD. But that's not what I mean. Her appearance on the list relates to her prominent appearance in the Silverpine quest line, in which she completely humiliates an entire Alliance race the second they open their front door, forcing them to live in a tree. With elves. This is immediately followed by the unique moment of all racial leaders in which she proves that death itself isn't enough to stop her anymore. The Banshee Queen's influence is now impossible to ignore, and few other characters in the game get discussions as involved as those about her methods and character.
The "too soon" appearance of Ragnaros in the Molten Core was a big moment for Vanilla players, but it was often stated (including by Blizzard) that a group of level 60's could not kill an Elemental Lord at full strength. Given the home-field advantage, Ragnaros should crush most mortal opponents like the gnats they are to him. And, when he came back in Firelands, this theory was put into practice with pretty convincing results. More than any other end-raid boss in the entire expansion, Ragnaros was a "wall" that stopped raids and guilds in their tracks. The difference between the guilds that went 6/7 versus 7/7, ESPECIALLY in heroic mode, was massive, a huge jump in difficulty that, in many cases, led to frustration and outrage. Whether or not you saw him walking on legs, Ragnaros demanded the respect of all those who faced him.
This one's a no-brainer. How often do you get to save the universe and also get the girl in your very own cutscene?