I was going to make a topic on this actually, never got around to it. So thanks!
Spoiler:
I know the reaction towards Katy Perry can either be extremely positive or extremely negative (no in-between), but this song really impacted me at an important time in my life. Won't go into great detail since it's personal, but just an absolutely beautiful song. I have trouble listening to it from time to time but that won't stop me from listening to it lol.
Pray and HANABI by Ayumi Hamasaki fuck me up too. As well as infection by Chihiro Onitsuka.