Some of the blood elves and pretty much all of the pandaren. That's about it.
I'll explain the easy one first: I love the pandaren because:
1. They live on a giant, sentient turtle whom they clearly love very much and with whom they are able to converse at need (although the game makes it seem like there's a bit more effort to it than three or four hours of gaming would have you think...)
2. They don't seem like they have a very strict leadership - from what I've seen in the starting zone quests, it looks like they're led by whoever the oldest pandaren alive at the moment happens to be. Even if this isn't true, there is an insane amount of respect for their elders that isn't readily apparent with most of the other races I've played, and it's a refreshing change of pace to see that cultural element be so strongly interwoven with the actual game play (especially since, even with the tauren, any other race with a strong respect for their elders only seems to display it in the lore and very rarely in-game, if at all).
3. Pretty much their entire culture and belief system (as much as I've seen of it, anyway). I love the 'hello' and 'goodbye' quotes they give you ('Slow down; life should be savored!'), I love their focus on the betterment of one's self as well as the protection of one's people (rather than, 'You or your loved ones? Choose!'), I love how connected and ACTUALLY symbiotic they are with their surroundings (even Ji doesn't want to wipe out all of the hozen, which is why he directs his strike at their leader), I love how downright peaceful they are... I seriously want to live on Shen-zin su, now. And I've only played pandaren characters for a total of eight hours.
4. They are so fluffy. So very, very fluffy. I'm ashamed to admit I love them for their huggableness, but it is definitely a factor in how much I love these guys.
5. You get to punch Varian upon joining the Alliance. WORST REASON HERE, but you would not believe how refreshing it is after having to say goodbye to those pandaren you've played alongside for twelve-ish levels and who chose to leave with the Horde - especially knowing just how awful the 'join the Horde' scene turns out to be (as far as I'm concerned)...
As for the blood elves, the reasons are a bit more complicated, mostly because there's a different set or each character. Fortunately, I only really have four favorite canon characters: Regent-Lord Lor'themar Theron, Ranger General Halduron Brightwing, Grand Magister Rommath, and Archmage Aethas Sunreaver.
As far as Lor'themar is concerned, I have lots of reasons that really focus more on his personality than on his actual appearance (although, uh, there's something a bit fetching about the whole silver-haired-and-missing-an-eye thing, and I'm pretty sure he's the blood elven equivalent of a forty-five-year-old, so there's that...) Also, he's the only one whose good traits I already had written down, so he's the only one with a really extensive list at the moment~
To start with, Lor'themar comes across to me as being very fatherly towards those he leads. From what I've seen and read, he doesn't just look on them as "his people," he really does behave as though he understands that he is their ultimate defender and is willing to do, in his own words, "whatever it takes to protect Quel'Thalas and its people." In my mind, there are few figures more worthy of respect and admiration than those who feel as unfit for their position as Lor'themar seems to, yet willingly take on the mantle of the protector and leader for the sake of those people they claim as their own. Lor'themar wants nothing more than to go back to the days when he was a simple Farstrider, yet he does not once shirk or shrink from his duties as the Regent Lord, and to me that is a powerful thing to witness.
Additionally, he's sensible. He's not just practical, he's not cold and clinical, and he's certainly not impetuous; he actually sees and feels what his people are made to go through, understands what they want and what they expect, and is able to see and choose what he believes to be the most reasonable road to walk at the time, even if that road is painful for him. And he tempers that with a rare (for Warcraft leaders, anyway) understanding of what others deserve, despite how he feels about what they've done. Take his mission to the Quil'lithien Lodge in "In the Shadow of the Sun", for example: he went there not only because they were once his friends, not because he expected a warm welcome, but because he knew whether they welcomed him with smiles or blades, they were once his people, too, and they deserved to know that Kael'thas had died a traitor and that the Sunwell had been restored. That takes a lot of courage, especially considering how against the trip Rommath and even Halduron were.
Combine that with the way he reacts to Aethas's request in Shadow: Lor'themar carries the same anger as Rommath and Halduron, but Lor'themar does not jump into an argument with anyone over what the Six could have or should have done, nor did he allow his feelings to sway his decision overmuch. Instead, he essentially left the choice up to his people: you can fight under the banner of the Kirin Tor, or you can stay out of it under the banner of Silvermoon. Considering the emotions and the history between the sin'dorei and the Kirin Tor, I think he made the least explosive decision available to him, and I'm impressed at how easily he picked it out... even if it was partially to get on Aethas's nerves. And he didn't waffle - he made his decision and he stuck with it.
As a matter of fact, the whole story in Shadow really showcases to me his ability to separate his own thought process into sections - to detach himself when he needs to and see things from his own standpoint and still see the bigger picture. He doesn't easily allow himself to be swayed by his own emotions - or the emotions of those such as Rommath - which I think makes him a much more reliable leader than, say, Kael'thas, who's a bit infamous among the fanbase for having a somewhat quicker temper. At the very least, Kael certainly vented more passionately than we've seen Lor'themar do so far, and in my mind some emotions are better left controlled (as Lor'themar does beautifully) than spoken aloud for your followers to hear (as Kael'thas did once or twice even before he joined forces with the Illidari).
And, of course, there are tiny, less important things, like the fact that he's missing an eye and gives few - if any - indications that he even notices it at this point; the fact that he wields a kickass two-hander in one hand; the fact that he is the rare white-haired pretty boy who has not turned evil; and the fact that he was a Farstrider long before he was Regent Lord.
As far as Halduron goes, I love him more because he is able to act as a voice of reason when Lor'themar needs to bounce his thoughts off someone; he very easily slips into the role of silent supporter (again, I'm referencing Shadow here); and he has the ability to read Lor'themar well enough to know when arguing with him isn't going to work (not that this necessarily stops him from doing so every time...)
Pair that with Halduron's hotter temper (I have to admit, where I dislike it in leadership roles, I love it in generals and archmages) and his ability to make what he believes are intelligent militant decisions regardless of what Rommath might have to say about it, and Halduron's an appealing character for me. I just wish there were more canon sources involving the man...
With Rommath, it really comes down to his loyalty to his people - even over the prince he very clearly would have followed to the grave, had certain events not taken place. My Country, Right or Wrong might be an irritating trait to put up with sometimes, and Rommath is definitely old-fashioned when it comes to the traditions of Quel'Thalas's leadership, but he's an admirable character for it - even if he is as snobby as a magister can get sometimes. Plus, he has long hair. I live for men with long hair~
Aethas is pretty much the hotshot kid fresh outta college, at least as far as the others are concerned. I like that he's got spunk, even if he is a bit childish in comparison to Kael'thas. I also think he gets some of the worst rotten luck - not only do he and the rest of the Sunreavers get forcibly removed from Dalaran, but Lor'themar manages to lose his cool just long enough to (essentially) publicly demote/humiliate the poor man. Aethas needs a hug and more fans. And then he and Rommath need to sort out their issues with each other so that they do not have to spend every minute in each other's presence fighting like cats and dogs.
I also have a bit of a soft spot for Magister Astalor Bloodsworn, Lady Liadrin, and Voren'thal the Seer, but more than anything the only reason I even started to like them is because of wanda von dunayev, who is a demi-goddess of fanfiction writing.
I also have a soft spot for Koltira and Thassarian, but that's more of a fanon-induced soft spot than a canon-induced one. They make the world's most adorable undead pair...
/end book.