While most settle for humorous mash-ups, and some get friends and family to rush through an assortment of scenes, some manage to find a truly ingenious, fresh angle that encapsulates the essence of the film in miniature form.
Some of my favourites:
There Will Be Blood re-imagined as a video game which retains pretty much the entire plot, down to the milkshake
Inception, distilled in paper cutout animation
A very clever Social Network parody
Lego Die Hard
Borderline inappropriate, but clever & funny: Titanic in a bathtub
All Lee Hardcastle's claymation shorts are amazing. His take on The Exorcist is pretty funny.