I nominate Cool Hand Luke. It is the greatest movie ever made and perhaps the greatest creation in the history of art. You can watch Cool Hand Luke on your computer by using the "watch now" feature on netflix. I keep it on constant loop when I am online at home and work - - I'm sure this is very common and will allow for multiple viewings and a lot of discussion.
I also nominate this DVD -
http://www.netflix.com/Movie/Age_of_...1134052248_0_0