Top ten dialogue-free* openings in films

Aside from Steve Reich, the coolest person to ever wear a baseball cap...
Harry Dean Stanton in Paris, Texas

1. Once Upon a Time in the West (Sergio Leone, 1968)
2. 2001: A Space Odyssey (Stanley Kubrick, 1968)
3. Paris, Texas (Wim Wenders, 1984)
4. Wall-E (Andrew Stanton, 2008)
5. Touch of Evil (Orson Welles, 1958)
6. Up (Pete Docter, 2009)
7. Aguirre: Wrath of God (Werner Herzog, 1972) 
8. Eraserhead (David Lynch, 1977)
9. There will be Blood (Paul Thomas Anderson, 2007)
10. Le Samourai (Jean Pierre Melville, 1967)
 
It's a bold move for any film-maker to have no dialogue at all in a five, ten or even twenty minute opening sequence for a film, but it can set the mood of the movie perfectly, and besides, film is meant to be a visual medium. The opening sequence of many of these films is the best part of them: Paris, Texas would have been great as a ten minute short film; once the dialogue and story begin, all the mystery and beauty vanishes and the film turns very average indeed.

*Mostly