For me, there are two that come to mind. The first is the anime Clannad and the second is the book A Thousand Splendid Suns from Khaled Hosseini.
Clannad opened my eyes to the full extent a work can touch your emotions through its characters. Up to that point, every anime I watched was the standard shounen fanfare, like Naruto and Dragon Ball. But this one story made me change my view on the world and life itself. I remember feeling an emptiness inside when it ended, knowing an experience like that wouldn't come as easy.
Little did I know right around the same period, during my high school years, I would be proven wrong. I took a lot of books from my school's library and always had a good relationship with the librarians. One day, this one book by an author I had never heard about caught my eyes. I saw how no one had picked it up yet and asked the librarian about it.
She told me it was an amazing experience and that I should give it a try. When finishing the process, she confided me she cried rivers with the letter part. I didn't undertand what she meant at that point.
Untill I reached the letter. And I felt the biggest surge of emotions in my life.
I think THAT was the day the seeds of wanting to be a writer came from. I've read many other books in my favorite genres, but nothing came close to how I felt. If I can touch 1 person in the world with my work the same way Hosseini did with me, I'll know it was worth it.
So, if you interested, here's my story. And also, what's your life changing work?