Which Message and Why?

Hey guys, T4G was great.  I was wondering if you could say which message most impacted your life and ministry and why.  For me, I would have to say Piper's.  I have already listened to it again and it just drives me to go and preach the gospel.  I have been quite convicted on how easy it is to live like the world.  I want to impress the world with the gospel.