Favorite plot theory you think actually stands a chance of being canon:
That McGonagall is working for Voldemort and has been from the start.
Favorite plot theory you think has no chance, or very little chance, of being canon:
Hmnh. I should probably also go with the McGonagall theory here, since most people think there is NO WAY she could be evil. But instead, I'll say that I sort of enjoy the theory that James never did "reform," but somehow forced Lily to marry him (yeah, I'm a sadistic little thing, what of it? ::grin::). But I don't think JKR would EVAH do something like that in canon.
Plot theory you HATE and think actually stands a chance of being canon:
ARGH! LOLLIPOPS!! Snape never ever EVER loved Lily! It turns my stomach. And JKR will in all likelihood go there. I'm also not particularly fond of Ron/Hermione, which to me is obviously going to be canon. But I don't hate it . . . I just don't really like it much.
Plot theory you HATE and just KNOW that JKR would never go there. NEVAR.:
That Harry will have to kill Voldemort by the end of the series. I know most people think this is a given, but I DON'T want my Harry to become a killer, and I hopehopehope that JKR feels the same.
Plot theory that tickles your fancy, but you aren't completely sold yet:
Ron=Dumbledore. I think it would be way cool if it's true, but I'm just not sure I think she'll go there.
Plot theory you'd like to hear more about:
Can't think of one off the top of my head.
Where do you stand on ESE!Anyone? These theories usually revolve around a seemingly 'good' character who has been evil all along. The most common ones are ESE!Snape, ESE!Lupin, ESE!Dumbledore, ESE!Tonks and ESE!McGonagall. ESE stands for 'Ever So Evil'.
I love speculating about ESE characters. I *strongly* believe that someone we trust will turn out to be evil near the end of the series. For that reason, I don't think it will be Snape (not everyone trusts him, and I mean readers not other characters in the books). Lupin is a possiblity - there's some great canon to point to Lupin being evil, but I don't like it and I've decided that it's *not* going to happen. So, as I said above, my money is on McGonagall. I have lots of canon to back up this decision (you'll find a write-up of some of the evidence here), but people often say, "oh - it CAN'T be McGonagall." Which is, IMO, the whole point. If JKR wants to spring something BIG on us, it doesn't have the same impact if it was obvious or easy to guess. So, I think McGonagall will prove to have been working for Voldemort all along. That would be big. :-)
Wacky, off the wall theory you just can't help seriously entertaining:
That Lucius is somehow going to get himself out of prison, kill (or otherwise dispose of) Fudge, and become Minister for Magic. Oh! And I'm pretty sure that Rita Skeeter is really a man.
Make a prediction for Book Six Harry Potter and the Half Blood Prince
Hagrid will inadvertantly betray Dumbledore, leading to Dumbledore's death.
Who is the Half Blood Prince?
Tom Riddle. But I don't feel particularly strong about this. I actually liked the idea that it was going to be Mark Evans. ;-)
Will the final revelations in Book Seven shock and amaze us? Will there be giant plot twists we never considered?
I sure hope so. And I do think there will be huge surprises (well, not for me, since I already know McGonagall is evil ::grin::) . . . but I think that perhaps we will have been able to guess the overall conclusion, but there will be twists and turns that we won't have anticipated.
Who do you think is marked for death?
Dumbledore, Hagrid, Fudge (although he might not die - he might just get thrown out of office), one of the Weasleys (but not Ron; Percy would be the easiest to handle; one of the twins would be the worst), almost certainly Snape and very likely Lupin (although I'm filled with dread at the thought of losing either of them); McGonagall and Peter. I'm also not entirely convinced that Harry will survive, but I sure as hell hope he does.
Prediction you would bet your first born (or at least a wad of cash) on:
Arthur Weasley will be Minister for Magic by the end of the series. (And I've been saying that since before Ron made his "prediction" in OoP).
And now for a shipping prediction... Who do you think Harry will end up with in the end, if anyone?
Hmnh - I honestly don't think he'll end up with anyone in canon. He'll be going through too much. Besides, how many people have chosen their lifelong mate by the time they're 18? If he does end up with anyone though, I hope it's Ginny.
ETA: I forgot a couple of other favourite theories when reading one of the other responses to the meme on Helen's journal . . . I believe that Arthur was under Imperious during VW1, and also that Molly and Arthur had a child ( born between Charlie and Percy) who was killed in that war. If you really want angst, then Imperious!Arthur is the one who did the killing. ;-)