First trailer for Star Wars from 1976 JUL 07 2014
In 1976, 20th Century Fox released a teaser trailer for a little film called Star Wars...aka "the story of a boy, a girl, and a universe".
No James Earl Jones voiceover for Vader, no John Williams score (which wasn't finished until just two months before the film premiered), but those visuals must have impressed.
Here's the first teaser trailer for Empire Strikes Back, which features no film footage at all, just concept art drawn by Ralph McQuarrie:
And for the sake of completeness, the teaser trailer for Return of the Jedi, which appeared in theaters before Lucas changed the name from Revenge of the Jedi: