I can't list just one. It changes from day to day. "The Opening of Misty Beethoven" comes to mind immediately, and then there's my own "The Hotel Shoot" (http://www.afterglow-photo.com/aftvids.htm), but I suppose you're asking for nonporn Hollywood movies. Here are a few faves:
Alien (seeing Ripley in her skivvies with the monster literally feet away was a formative experience).
House of Games (Lindsey Crouse plays a psychotherapist who becomes a bit too fascinated with Joe Mantegna, the leader of a crew of con artists).
The Fifth Element (one of the ten best sci-fi movies ever made).
Blade Runner (easily one of the ten best sci-fi movies ever made, especially the Director's Cut).
Wings of Desire (the German film upon which the much inferior City of Angels was loosely based).
There is a documentary about the life and work of Frank Lloyd Wright which I can watch over and over. (I don't know if you've ever thought about it, but FLW is probably the only American visual artist who can pretty much undisputedly claim to be the best in his field.)
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