okay, so this isn't a trailer, but it's one of my favorite shorts.
this 3-minute love story was created using stop motion, which is an animation technique that makes objects appear to move on their own. (think Robot Chicken.) the simple explanation is: you take an object and move it in small increments, photographing each frame. this creates the illusion of movement when all the frames are sequenced together.
if this still sounds weird, just think back to when you were a kid and you used to take a small flipbook and draw inside every page, then flip all the pages real fast so it looked like the drawing was animating. that's the same thing, sort of.
anyway, check it out:
the artist's description of the piece is: "A couple of pencil-outlined birds escape from a little girl´s drawing, leading us through the life she dreams of."
so how does it relate to movie trailers? because it's a great example of how to tell a coherent and moving story in very little time, using the trailer-maker's best tools: music and visuals. even without dialogue/VO/text, the story still comes across perfectly. and the lack of words lets it transcend language, making the piece universal.