I'm just going to link this here in case by some miracle you haven't seen it. Marvel had to drop the first trailer for Avengers 2 a little early due to a leak, so now we have the official hi-definition version:
I like this trailer because its a bit hard to piece together what the story's going to be, or how it will all fit together. We know this much: lots of Ultron, probably a Stark experiment gone horribly wrong, signs of Quicksilver and Scarlet Witch, a traumatized Banner, and lots more. Oh, and the Hulkbuster suit shows up, too....fascinating!