1. The character you first fell in love with:
First fell in love with? Does that mean it has to be someone from the first book, or can it be the person I fell in love with immediately after introduction? I'll answer for both.
First, sadly, it was probably Fred and George. I mean, I liked Harry a lot, but I wouldn't say I was completely in love with him from the get-go. But Fred and George amused the hell out of me from the moment they first appeared, and after OotP, how can I NOT love them? (This is not to say they're my favorite characters, but the question isn't asking that. =p)
But, to answer the second part, I truly fell in love with Lupin after he was introduced. (Okay, after he woke up.) Even my other favorites I didn't like quite as much right off the bat. I can't even say why I loved Lupin so much so quickly, but there you go. It's a deep abiding love, what can I say?
2. The character you never expected to love as much as you do now:
Ginny! I mean, she's barely in the first one and not all that great in the second, since all she really does in that one is get possessed and crush on Harry. She doesn't do a whole lot in the third one either, really, so she was just kind of "Ron's little sister who likes Harry and got saved by him once". She starts picking up some in the fourth book (QWC, the ball, etc.), but she blazes into the fifth one as soon as she's introduced, with her casual lying to her mother and all the way to going with Harry to the ministry. She's suddenly a lot more alive, and it's especially cool after the way she was when she was little - you can tell she's dealt with what happened to her and is all the much stronger (and cooler) for it. I love her to pieces now.
3. The character everyone else loves that you don't:
I'm going to have to agree with zaph and say Draco Malfoy. He's a cowardly, spoilt little asshole who isn't even cool about his evil. At least his father can sometimes be entertaining. Of course, some of my hatred for him stems from the plethora of people who don't like Malfoy, but rather fanon!Malfoy, who's actually a tragically misunderstood (and gorgeous) hero, or something like that. But in canon, he's just a conceited little wanker.
4. The character you love that everyone else hates:
Gods. I don't think Ginny counts, even if a lot of people don't seem to like her. Hmm. I have no idea how people feel about him, but I really like Tom Riddle (not Voldemort, but that 16-year-old who would be Voldemort). I mean, damn, he was creative about his evil. He was also still human, which actually makes him more interesting than Voldemort, in my opinion.
5. The character you used to love but don't any longer:
Uh... I can't actually think of anyone I used to *love* and don't any longer. I mean, I used to sort of vaguely like Cho, and now I can't stand her, but I'm not sure that counts, as my initial impression of her was sort of nonexistent. I still REALLY like Sirius, but I did get vaguely annoyed at his portrayal in OotP, because he was, like, totally different from how he was in GoF. But I suppose it's understandable, so I don't think that counts either.
Oh wait, I know. It's Mrs Weasley. At first I liked her; she's a lot of fun and a good mother and all. But now, her distrust of anything Muggle bothers me. I personally thought Mr Weasley's idea of using stitches was brilliant, even though it didn't work. The fact that she freaks out about him even trying it, just because it's a Muggle thing, bothers me. It's like... no, she's obviously not as bigoted as the Malfoys, for example, and has no problem with Muggle-borns. But she IS prejudiced, and that can still be a problem, especially because distrusting anything Muggle distrusts a lot of wizards' heritages. I also can't stand how gullible she is sometimes (like after Rita Skeeter's article, she turns all bitchy at Hermione for awhile when she should damn well KNOW that Hermione wouldn't do anything like that). So, yeah.
1. The pairing you first fell in love with:
It's all about the Ron/Hermione, baby!
2. The pairing you never expected to love as much as you do now:
Remus/Sirius. I was completely against HP slash in any form (mainly because none of it made sense to me, and though I loves me the slash, I am not about canon rape for slash's sake) for a long time, long after the second movie came out. Then, what was it... oh yes, I read the whole MST of the books thing this one chica was doing (what's the link, zaph?) which included R/S as a side thing (it also includes Harry/Draco, which I am still ADAMANTLY against, but that's not the point). I didn't fall in love with it then, but I realized it didn't irritate me as much as other HP slash pairings, and then, fatefully, mentioned the pairing to joellehart, who took it and ran. And found Canis M. and made me read it.
And I fell in love.
Now they're my happy place, sadly. Reading stuff about them makes me feel all warm and squishy inside, and as zaph pointed out, canon actually supports them, so I don't even have to feel bad about it. ^_^
The other one is James/Lily, because I actually find them just adorable now.
3. The pairing everyone else loves that you don't:
Harry/Draco. I mean, what the hell? They hate each other, and you know, hate does not equal concealed true love, no matter how much you may want it to. Plus, you know, Malfoy's a conceited fuckwit. Another one is Snape/anyone, because I have difficulty seeing Snape as even having sexuality, even though I know he must, somewhere. I suppose it's more I have trouble seeing him ever acting on it. But people apparently think Snape is Alan Rickman, and it's TEH SEX to have him making it with various other characters. I just shudder.
4. The pairing you love that everyone else hates:
Good lord. My pairings are actually very canon and/or popular, for the most part. I suppose I'll go with Harry/Ginny as well, because I just love that pairing now (see above, re: Ginny). She really is the only one who can knock sense into CrazyCapsLock!Harry at times, and her brand of calm and crazy is kind of what he needs, more than what Luna or even Hermione can offer.
The guilty pairing I like is probably Harry/Ron, which I think can be cute, but as I adore Ron/Hermione and Harry/Ginny, it rather takes a backseat to them. I also don't really see it as happening in canon. I just like reading it sometimes. ^^; And, you know, it COULD happen.
Oh! And Hermione/Ginny, because I think the idea of them experimenting with each other while their respective future boytoys are being clueless is incredibly cute. But I don't see that one as lasting much beyond that, either.
5. The pairing you used to love but don't any longer:
This one doesn't really apply, because I never was into pairings early on, and so all the ones I have now are recent and I still like them. For that reason, we'll go with Harry/Cho, because I wasn't opposed to it or anything before. Now I am. ^^;
That was far too entertaining.