One of the earliest films jam packed with suspense without sound
http://www.imdb.com/title/tt0015648/
Watch some old silent movies (Keaton, Chaplin, Lloyd) for ideas on suspense. Agreed, sound and music are important, but editing plays a big part in what the viewer deems suspenseful.
Nosferatu does a good job as well for no sound.
http://en.wikipedia.org/wiki/Nosferatu
I love the way they substitute cymbals for waves at the beginning. By the way, this clip would be a lot less suspenseful without the music. : )I hate to nit-pick, but score/music is sound.