I'll do it for Bleach, Naruto, and Gundam SEED, because really, those are the only series I have a fuckload of pairings for.
"One True Threesome" ship:
Naruto: Although I ultimately prefer Team 7 as I see them in canon (Naru+SasuSaku with the occasional hint of more-than-platonic feeling from Naruto), I'm going to have to go with Naruto/Sasuke/Sakura here, because it's, well, the threesome of the series.
Bleach: Rukia/Ichigo/Orihime. This one is hard to find, because man, there's almost nobody in the fandom who can tolerate both IchiRuki and IchiHime. But afjdksl, Orihime would be so cute in a threesome, and she and Rukia together are what Ichigo needs, and I like both pairings, and I also think Rukia/Orihime would be cute. D: Somebody should write this.
Gundam SEED: This series is the home of The OT4, not a threesome.
Naruto: Uh. Yoshino/Shikaku, I guess? Fawn abuse and all that.
Bleach: Byakuya/Hisana, I suppose, if only for Byakuya being a giant dork.
Gundam SEED: Mwu/Murrue. Can there be any doubt? I think not.
"Not quite canon but should be" ship:
Naruto: Ino/Chouji. Here's hoping.
Bleach: Karin/Chad. What. They need more interaction so that they can be canon.
Gundam SEED: Guess what? All the awesome ships are canon! And that includes Dearka/Miriallia. Suck it, Dearka/Yzak fandom. But I guess I'll put Murrue/Natarle here, or more accurately Murrue<--Natarle. Technically Natarle has a crush on Mwu, but she should have a crush on Murrue.
"If this happens I'll stab my eyes out with a spork" ship:
Naruto: Naruto/Sakura. But less because the pairing itself sucks and more because it would fuck up the Team 7 dynamics, and also the fandom sucks ass.
Bleach: ...I don't think there's any pairing in Bleach that really pisses me off, at least when it comes to possibilities in canon? Haha, maybe Renji/Tatsuki.
Gundam SEED: Athrun/Meyrin. You don't fuck with The OT4.
"You are one sick bastard" ship:
Naruto: Kakashi/Naruto. afjdskl no.
Bleach: Urahara/Rukia. Why do I keep running across this in J-fandom.
Gundam SEED: Mwu/Kira. Make it stop.
"I'm one sick bastard" ship:
Naruto: Itachi/Sasuke. Everyone gets to molest Sasuke, even when it's horrible and wrong.
Bleach: Ishida/Nemu. It might not seem sick at first, but think about how she'd experiment on him!
Gundam SEED: Fllay/Lacus! ...what.
"I dabble a little" ship:
Naruto: Kabuto/Sasuke. It's totally hot, but somehow I never seem to get around to writing it. Too busy having Naruto and Sakura molest Sasuke, I guess.
Bleach: Ishida/Orihime. I was too busy cooing over TatsuHime to really notice this one at first, and then I was too busy seeing the canon build-up for IchiHime, but it's hard not to like IshiHime at least a little. They're such cute crack.
Gundam SEED: Athrun/Kira. All the
"It's like a car crash" ship:
Naruto: Orochimaru/Sasuke. So horrible and wrong, and yet I can't look away. D:
Bleach: Byakuya/Rukia. It would be so very wrong for both of them and so appallingly pretty and plausible.
Gundam SEED: Fllay/Kira. And I like it that way.
"Tickles my fancy but not sold quite yet" ship:
Naruto: Neji/Gai. I am totally sold on them being awesome in general together, but I have trouble feeling the romance.
Bleach: Gin/Rangiku. But you're getting there, ceylon. :*
Gundam SEED: Yzak/Shiho. Yzak's the fandom ho for me, but he needs people with personality. Prove to me that Shiho has a personality, and then we'll talk.
"Makes no canon sense [YET] but why the hell not" ship:
Naruto: Temari/Sakura. I can't even explain this one, that's how awesome it is.
Bleach: Actually, all of my favorite Bleach pairings make at least some degree of canon sense. I guess I'll go with Yoruichi/Kuukaku. They manage to have sexual tension even when Yoruichi is a cat! Okay, so Yoruichi has sexual tension with everybody.
Gundam SEED: Fllay/Yzak. I'm telling you, these two are the biggest bitches in the entire series. They're meant for each other.
"Everyone else loves it but I just don't feel it" ship:
Naruto: Kakashi/Iruka. Let's have a resounding "meh."
Bleach: Renji/Rukia. I know, I know, it's totally canon, but I just...did not feel the love. Maybe on the reread!
Gundam SEED: Athrun/Lacus. They managed to have no romantic tension whatsoever despite being engaged.
"When all is said and done" ship:
Naruto: Temari/Shikamaru. SasuSaku may be the one I expend the most energy in ficcing and arguing for, but TemaShika is my favorite. They just connect so effortlessly. ♥
Bleach: Do you even need to ask? Yoruichi/Soi Fong.
Gundam SEED: I'm evenly split between Mwu/Murrue and Dearka/Miriallia for my favorite individual pairing--Mwu/Murrue for the beauty of the canon, Dearka/Miriallia for the UST and all the possibilities--but in the end, the series comes down to Athrun/Cagalli and Kira/Lacus.
"Guilty Pleasure" ship:
Naruto: Lee/Tenten. It's used as a sideship by NejiHina/NaruSaku fans, and I have so many friends who love NejiTen, but--they're so cute! How can I resist!
Bleach: ...I have to pick one? All right, fine, Rangiku/Izuru. Yeah, yeah, she's meant for Gin, but! Drunken antics!
Gundam SEED: Dearka/Yzak. The fandom makes me want to strangle things, but I'm up for shipping Yzak with damn near anybody.
"I can't believe I read it and liked it" ship:
Naruto: Uhh. One of my favorite genfics has vaguely Anko/Sakura implications? Oh! I know. Hanabi/Hinata. Although it was childish and one-sided. Oh, wait--Kankurou/Shikamaru. Sort of.
Bleach: Chad/Karin/Rukia/Renji. And then I wrote an epilogue to the fic in question.
Gundam SEED: Blue Haro/Green Haro. Yes, really.
Favorite "Older/Younger" ship:
Naruto: Kakashi/Sasuke. Mmm, delicious twisted teacher/student not-quite-parental dynamics!
Bleach: Rukia/Ichigo. Well, think about it.
Gundam SEED: ...no, not really. Probably the closest I come is Klueze/Yzak, and Klueze isn't allowed to have sex. If he did, he might stop hating life and humanity so much.
"My first I could never abandon you" ship:
Naruto: Tell you the truth, the very first pairing that leapt out at me and made me go, "Yeah, that needs to happen," was Naruto/Hinata. And while it may not be the most exciting pairing out there, it's still my favorite for both characters.
Bleach: Tatsuki/Orihime. Admittedly, I was already shipping IchiRuki after the first chapter, but TatsuHime was the first pairing to totally own me. And as cute as the various other Orihime pairings are (she's the Little Black Dress of Bleach), I will always adore this one.
Gundam SEED: Mwu/Murrue. They owned me before the series even started really hinting at the romance in canon.
Naruto: Sasuke/Sakura. It is pretty much the essence of devotion.
Bleach: Yoruichi/Soi Fong. Duh.
Gundam SEED: Kira/Lacus. She fights a war to be able to live with him in peace.
Naruto: Lee/Hinata. For the win.
Bleach: ...I actually don't have any ships of this type for Bleach. This must be remedied. Kuukaku/Keigo? Discuss.
Gundam SEED: Haven't got one for this series, either. The closest is Fllay/Yzak, and they did meet. Score.
Naruto: Jiraiya/Tsunade. It's got Jiraiya. It's going to be pervy.
Bleach: Yoruichi/Urahara. It's got Yoruichi. It's going to be pervy.
Gundam SEED: Anything involving Lacus in pink latex and sparkly stiletto heels, wielding a whip with flowers on it.
Naruto: I'm going to be predictable and say Naruto/Sasuke, because you know, it is the most important single relationship in the series, even if I ultimately prefer it platonic.
Bleach: Chizuru/Tatsuki. In jello!
Gundam SEED: Athrun/Yzak. The fun part is that Yzak always loses!
And now I sleep. Writing that up took way too long. I suck.