None, really.
I don't think any one film ever changed my life. But, there is a film that (together with several books) started to change the way I think. That film was What The Bleep Do We Know. When seen as a true film, it's crap, but when seen as for what it is, namely a darn interesting documentary, it's really... erm... darn interesting! Of course, recent films like Big Fish, Magnolia and Eternal Sunshine Of The Spotless Mind also kind of changed my views about Life, the Universe and Everything. I wouldn't know what films before those ever did that to me. They don't tend to stick very long with me, really.