Needless to say, this is a tough decision. Each of these is an amazingly sad moment, well crafted by Tite Kubo. I side with Ulquiorra's dead for a number of reasons, but the central one is how it hits me. Ichigo's memories of Masaki are incredibly painful, but we're distanced from it to some extent, since it's treated as background material. We never actually meet her in any meaningful way. Gin's death is sad on multiple levels, especially since we knew so little about him, but that also works against it, making his death seem strange. We had very little emotional attachment to his character, aside from what we felt through his odd relationship with Rangiku.

Ulqiuorra's death, as I said on the last version of this question, was equal parts beauty and sadness. We always had some distance from Ulqiuorra, but that was built into his character. He was someone who could not understand human beings and the way they acted, something he only grasped as he died. Orihime's reaching out to him as he dispersed into dust is one of the most memorable scenes of the series, and with good reason. She was always beyond his understanding, always out of reach. He was an incredibly tragic character, and the tragedy was only enhanced my his sudden epiphany.

I'm close to seen that part I wil see if it sad or not

I think the saddest one is Senna's fading out in Bleach: Memories of Nobody.
The choices from the anime just hard to make a decision of a single one.

I nearly cried while reading about it in the manga! T.T but the other two were really sad too!

Heartbreaking T_T

it was a very sad scene.............gin's fall.............and rangiku's tears..................and rangiku thinking abt gin after his death..................aaaaaaaaaaw it really touched my heart.............hmmmmmmmmmmm

I found them all sad, but this one the most sad... Ulquiorra dying just wasn't played out sad enough in the anime, whereas the way Gin's death was played out actually struck me as more sad, even though I liked Ulquiorra a little bit more than Gin.

i know same here,..........rangiku's tears thats making my heart break more.............

Ulquioorra's death was very sad