Might sound weird, but one of the biggest moments for me was the Bloody Banquet, when the WoL is framed for regicide. IRL I've never been framed or accused of murder of any kind (thank God) but my life wasn't exactly a bed of roses. Being a loner and an outcast growing up, I really felt it when the WoL became public enemy #1. The cinematic for Heavensward showing the WoL pound his fist on the wall in anger represented what I'm sure almost everybody felt during that scene.

The other biggest moments were, you guessed it, 5.0's finale and 5.3's finale. Amaurot remains my favorite dungeon. Emet-Selch is my favorite villain.