As a video editor, I must say that I have a lot of respect for the poeple who do those recut trailers. They're showing everyone the power of editing, something that usually goes unnoticed by the film pagans (no offense :P).

You see, the editor is usually the unsung hero in the production chain of a movie. In fiction, he will try to link the movie back to the original screenplay after the director went apeshit on it while shooting (not true for every director, mind you). He might also salvage a movie that had been seen dead on arrival once the shooting is done and the producer, director, etc. cried themselves to dehydratation while watching the rushes. There's a scene in De Niro's "What Just Happened" that portrays this exact situation, but sadly without giving credit to the editor. This is common, of course, cause by default, all the credit goes to the director.

By alas my editorial rantings about editing, let's watch ourselves some of the best fake trailers out there, shall we?

Shining
One of the most famous, and the trailer commonly known for starting the phenomenon. You'll never see Peter Gabriel's Solsburry Hills the same way after this :P

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Office Space
Turning a comedy like Office Space into a thriller takes a lot of talent... and a tad bit madness...

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Must Love Jaws
Two men, one shark... and a lots of love!

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The Incredibles
Dealing with death and their haunting of our world : a friendly family matter

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Brokeback to the Future
One of the only 2 "Brokeback Mountain" recuts that made me laugh, the other being the one with C3P0 and R2D2

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</div>I know there's a lot of excellent recuts out there, but these ones are my favorites.
Have any more to suggest?