For me, some of the saddest scene ive seen in anime history are from one piece, it usually involves character history. BWAHAHAHA

But seriously, i think Clannad, or kanon.

one piece definatly has me bawling more than anything else and even over the strangest things too ,from shu shu the dog watching his masters house burnt down to zoro about to get kicked to death by an admiral and there's nothing the crew can do about it...

But FMA is definatly a really good contender for weepy moments too!

Let's see.. I don't usually get caught up in sad moments during an anime, well with the exception of Both FMA series, when Maes Hughes get's murdered.. I always know it's coming, but man it's a kick in the gut every time.

Mostly for me what gets me are bittersweet or sad endings; for example, the end of Blood + where Haji may or may not be dead, and Saya must return to sleep; that's bittersweet, or the end of the first FMA where ED must basically pass through the gate to our side and be trapped there, in order to get AL's body back... That's sad.

But mostly that's what gets to me. I think a lot of sad moments I see during animes, probably get chalked into the clinical view of things for me, simply leaving it as; sometimes it can't be helped. Who knows?

The sadest moment for me was when Frieza killed Krillin! I was like ten and it was terrible, I definitely cried.

Krillin! god how many times did he die by the series end? i lost count!

surprisngly i remember i got pretty moved by Soul eater one time, it was when Crona went nuts and maka walked up and hugged her, was the first time anyone had ever touched her after being raised by her evil mother to be a physcopath and she just let it all out! that was quite moving for an anime that never took itself seriously at the best of times

Saddest anime hmmm...

not sad but depressing for me was Now and Then, Here and There (今、そこにいる僕, Ima, Soko ni Iru Boku)

Pokemon is sad...........it makes me sad because that show reminds me how harsh reality is and it makes me jealous. In there they don't have to worry about everything and all they do is throw some ballz XD

haha pokemon? hmm no i think about it, its a bit cruel, taking the poor animals from their natural habitats and forcing them to fight each other D: i might never look at it the same way again!

the pokemons can just run away and slack off(like snorlax and charizard) xD but they choose to fight

Claymore is a sad anime too. I cried when Teresa died T_T

Gantz.
i hated how i grew to like the main characters to see them get slaughtered like lambe