Axel, Xigbar and Xion's...and VEXEN'S.
Axel - Because of how emotional it is after playing through Days and...being so evil that I nearly CRY rewatching it again when I played through Kingdom Hearts. "He made me feel like I had a heart." AGGH. SO EVIL AND YET SO BEAUTIFUL!
Xigbar - For...just all the hidden glances and the subtle things that can revert back to his relationship with Roxas. After finishing my Xigxas essay, this is still one of my favorite death scenes. While it's short, it's sad and just has a pretty nice impact on the story.
Xion - CUS I CRIED THE FIRST TIME I SAW THIS. Because I actually like Xion, I liked her death scene, seeing Roxas that sad and the MUSIC. It's just like Axel's. Afdsdfgdfh. So wrong. ;3;
Vexen - Because it's dark, dramatic, and just all around AWESOME. 8D