Ghostface180

Opening scenes of There Will Be Blood

Mordred

Takashi Kitano's Hana-Bi (or Fireworks as it's known in America) has a lot of silence in it. Beat Takeshi's character maybe has a page full of dialog spread throughout the film and I don't think his wife has a single line. Many of the main characters spend long stretches alone or in silence.

rennervision

A perfect movie that shows how tense a scene can be with no sound is Mission: Impossible when Tom Cruise breaks into the CIA super computer.

GuessWho

Cop Land.... Stallone loses his hearing and we get a climactic scene from his POV (or is that POH?)

Geofferson

Riffifi jumps to my mind first.

TGM

Altered States?

Lastyear

Bergman's The Silence

chente

I'll second the recommendation of Naked Island. That movie is hypnotically beautiful.