Years ago, when I was just a little tyke, my parents bought me a book of Peanuts collected comics. One of the comics in that book was quite life-changing for me:
I must have read this when I was about 8 years old, and it has been in my memory ever since. So whenever there has been any thoughts about free will, this image and dialog always popped up. It's funny how a comic that I read when I was so young can still have a profound influence on my thinking today. It must be one of those "fundamental-truth" things.