Mine is Forrest Gump because of how well Tom Hanks plays his role and the movie seemed flawless.
The Butterfly Effect (2004)
Inspired , thought provoking, deep, tragic, great sound track.
Don't let the cast put you off- this isn't typical Hollywood and its not really a love story. It's a story of possibilities and alternative realities.
The sequels were pathetic- and Hollywoods attempt to try to cash in on a film they never really sanctioned in the beginning until it became successful.
https://www.youtube.com/watch?v=7Cz2Wn2-Aeo
https://www.youtube.com/watch?v=uGmVezpzO0I
I'd heard of that movie but couldn't place it until I found this: http://en.wikipedia.org/wiki/The_Butterfly_Effect
At the time, I didn't fancy the movie much at the time because I don't have a lot of regard for the so called butterfly effect, (it's hooey) and even less for the populist interpretation of it.
But after reading that resume and seeing a few clips, it looks interesting. I might keep an eye out for it.