mine would probably be...

Yume Tsukai
Welcome to the NHK
Air
Sola
xxHolic
and Clannad.

they're all pretty good :]

Well, I know which series had a terrible rather FAMILIAR plot..

*COUGH* Gundam Seed Destiny.

i always thought yume tsukai was just like any other magical-girl type anime, except with a different theme.

School Days definately has my vote for interesting and unusual.

Haha, Welcome to the NHK. That was such an odd anime.

Moetan is quite the odd plot.

yes please school days has the weirdest plot it became to love story to a total psychotic story

I would say melancholy of haruhi suzumiya

lol, agreed.

And for me, it's xxxHolic, The Melancholy of Haruhi Suzumiya, School Days, and Death Note (well, the manga at least, I don't know about the anime). I also thought Revolutionary Girl Utena was pretty interesting.

Sayonara Zetsubou Sensei <- definitely the weirdest out of all the ones i`ve seen xP.

School Days - err.. started out pretty generic & i think the person just wanted to end it quick so he killed everyone =_=? but wouldn't call it the weirdest - i`ve seen a lot of anime like this actually ._."

Ouran High School Host Club <- different plot to most anime i think; if not simply entertaining.

^ yeah. Ouran High School Host Club had a pretty interesting/strange plot. It was still entertaining though.

the serial experiments of Lain is the weirdest anime I've seen. the ending was highly unexpected.

I have a few ones I think are interesting:

Spirited Away - not your typical anime, its gorgeous and love the plot
Howl's Moving Castle - love everything about it
X/1999- despite the violence it was different

^ oh yeah. i think anything by Miyazaki is really..
wow.

Ouran High School Host Club - I loved this one, and I never heard of a host club so I thought it was pretty interesting. xD

Death Note - This one's very interesting. O__O;; Instead of the main character being a hero, he's a killer...( though he doesn't think of himself that way... )

Wallflower - I thought this one was interesting. xD;;; sumiko's funny, with all her horror stuff >.>;

Pucca - I guess Pucca counts as anime, right? right? xD This one's interesting to me...with all the kissy stuff going on between Pucca and Garu xD

Yoh Oo Bi - It' a Korean anime movie...I don't know if many people heard about it, but it's very interesting...kind of reminded me of Miyazaki's movies. xD

Spirited Away - Definently unique and interesting <3

Azumanga Daioh - funny and interesting. At least to me. xD

Lovely Complex - the most interesting romantic manga I have ever read xD

probably mind game, even if it is a movie. you can't beat getting stuck inside a whale while trying to escape the yakuza.

Sayonara Zetsubou Sensei <3 absolutely nuts, I love how each of the students has their own weirdo personality/quirks

definitely ouran host club~ oh and hana kimi has a pretty interesting plot to it =D

Probably for me would be:

Death Note (omfg the potato chip scene was amazing! I am still amazed even after a year later. how the hell do they come up with those stuff?!)

The Melancholy of Haruhi Suzumiya (words can't even begin to describe this anime)

Fooly Cooly (I've watched this like 3 times and still don't get it)

Sayonara Zetsubou Sensei (dark humor I suppose ...)

When They Cry (Ummm ...)

Death Note and Elfen Lied.

Most twisted plots ever.

I agree.

one of the animes where you actually need to have a brain to understand it. haha

death note
yeah.. it was definitely interesting
blood+
looool i just love these type of stories.. when they include science and stuff..
futari ecchi
more of unusual XDDDD

Kaiji...

if you all dont know what it is, give it a try on veoh.

deathnote

I don't think there can ever be an anime that is totally original because they all follow a certain archetype. However, what set Deathnote, which follows the archetype of detective work, from the rest is it's enriched content. It has a very nicely thought out plot and is very interesting.

i'd have to say Yami to Boushi to Hon no Tabibito
the beginning caught my attention then i got confused along the way

I think Death Note has the most interesting plotline. =)

Death Note,
Le Chevalier D'eon (HOOOKED!!!!!)
XXXHoliC

death note..most def
the melancholy of haruhi suzumiya <-- ridiculous, weird....and i couldn't stop laughing

one anime that really WOWED me had to be code geass.
it had so many insane plots, twists and turns that never ended until the end.

ouran host club and the melancholy of haruhi suzumiya were both unusual but really funny!

Mushishi
Death Note (though I haven't seen the anime yet)
Anything by Miyazaki, really.

Revolutionary Girl Utena.

A Female Prince trying to save a female princess. =)

Death note, the BEST story plot
Fury Cury (FLCL): The WEIRDEST

FLCL and c'mon guys... Neon Genesis Evangelion.

Serial Experiments Lain or Full Metal Alchemist. I know FMA is well known and all but the plot took a strange twist quickly and I never knew what was going to happen.

Oh god Monster!!!!!
It is, the most twisted, yet interestingly done plot ever! Like I was captivated by the creativeness of the author. It is so damned complicated it's almost impossible to summarize. I loved every bit of Monster to the fullest. Naruto and Bleach are NOTHING compared to it. If you haven't seen Monster, you have to watch it. There are so many twist and turns it's ridiculous... And the ending was...*sigh*
watch it!

and then Death Note. ^^

oh yeah, LOVED monster, f'n work of genius. Having said that, I actually think that 21st century boys from the same author is hm.... more grand in scale and equally complex.

i havent seen much anime but definitely Death Note has the most interesting plot!

deathnote
tsubasa chronicles- has a lot of twist!! specially about the story of syaoran and fye

Mm i would have to say FLCL is has the weirdest plot for sure
I also think Yu gi oh is pretty unusual o_O i mean what other anime involves a card game with a little boy who can instantly hit puberty and go back while fighting shadow realm..things all with cards

FLCL this is a strange'un for sure. o,o
Serial Experiments Lain Gah, I had such a hard time understanding the story =.=;; Just really confusing..

and.. Elfen Lied?

Mostly a lot are named here

I recommend with most interesting plot..

- MONSTERS; friggin awesome

and

Higurashi no Naku Koro ni

Ichigo 100% has a unexpected ending
Fullmetal Alchemist has an interesting plot
Oh yeah and so does Black Lagoon

i think wolf's rain had a pretty weird plot. beautiful drawings too.

MoonPhase... I've downloaded the first two episodes from iTunes, but I haven't watched the rest. o.O

But anyway, I thought it was pretty interesting and cute at the same time. ><

FLCL... take about unusual hahaha

Gantz... pretty unusual as well as interesting

Evangelion with the ACTUAL ENDING... INTERESTING!

I just finished watching Monster and I have to say it's one of the better plot-driven animes I've seen so far. A total of 74 epsidoes and not a single filler episodes... Episodes that make absolutely no sense and may seem like filler at first will eventually make sense and tie back with the main storyline later on.