Changed my life?
It's a difficult question, because I see life-changing experiences (in this case manga/anime/visual novel) as lessons for the most part. Almost all of the Vns and Mangas that I've read - I read for entertainment, so it's very hard to actually pick the ones that are awe-inspiring...
Hmmm, I know for certain that the manga named [Ai-Ren] changed me. I've never been in despair, I've never thought that death could be that close, I've never known what the true meaning of hope and life means. Reading this definitely made me rethink of what I've done, I am doing and I'll do.
As for VNs, I'll say that one of Akane Senri's statement in her route of the infamous Rewrite really made me thinking. Something like: "To make a decision does not only mean to choose something. It also means to give away something else." I'm sticking to that principle for life.