all cool characters that for the most part had their deaths due to the writers attempting to shock the readers. The only deaths above that had meaning were banshee and Pyro. But all characters listed above are awesome characters that add value to a story.
I would say that most of all, Destiny's death had meaning. She's been dead for 20 years and yet, she's still causing storyline's to this day! (Legion Quest, Age of Apocalypse, Destiny's Diaries)