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"Once upon a time in Nazi occupied France..." was a pretty great opening for a revisionist history yarn like Inglourious Basterds. I feel safe in assuming it's the most violent film to ever use the instantly familiar "Once upon a time..." line for story positioning.
Can you think of other films that have used the "Once upon a time..." line in unusual fashion? It's a memory exercise for the comments. The only movies I can think of are the original Disney classics which even used to zero in on books opening and turning pages to put you in the right fantastical (not based on a true story) frame of mind.
I know that Disney promises that the upcoming Thanskgiving release, the 3D animated Tangled, will be a "really fresh, smart take on the Rapunzel story" but I think nobody will ever beat Stephen Sondheim for refashioning fairy tales to serve his own brilliant purposes.