Carl, who sent us the tip about the trailer, called this "the most incredible Guild Wars 2 video [he's] ever seen." Well, I can see where he's coming from.
The video itself isn't long, but it's "Mega" for the sheer volume of the source material — it's a recut of several official trailers and timelapse clips, set to music, and it's really fun to watch. Gen Kim, the freelance video editor responsible, came up with the idea as a way to show off the game's design and animation. I'd say he succeeded.
Before you take a look, note that the trailer contains spoilers for season one of Guild Wars 2's Living World storyline. Noted? Good. Now go, enjoy: