Ridley Scott's Prometheus (Updated with Trailer)
(HD quicktime options available here)
For one thing, it echoes the brilliance of the original Alien teaser with the sound design (that haunting wail), but also by building the title line-by-line, which is awesome. This is goosebump city, and I can't wait to see it in a proper resolution.
This is my most anticipated film for 2012, being that Alien is pretty much my favorite sci-fi film, and my top pick for "most horrifying film of all time." I haven't liked many of Ridley Scott's more recent films, but this is looking excellent so far, even just based on the crappy cam teaser.
One thing I hope they fix before this is properly released is the grammatical error, "it's" instead of "its".