The Ultron trailer was fantastic, very creepy. Also managed to build hype without revealing too much either.
Also looks like we'll be getting a Batman v Superman trailer in the next month or so.
Original story from batman-on-film
At Comic-Con back in July, Warner Bros. showed off a quick teaser for Batman v Superman: Dawn of Justice. That was exclusive for the Comic-Con audience, but now it appears that Warner Bros. is ready to release a bigger trailer for the world to see.
According to Batman on Film, the first Batman v Superman: Dawn of Justice teaser trailer has been completed and is ready to go. BOF’s sources say that it will be attached to a November or December movie and released online around the same time. Warner Bros.’ sister company, New Line Cinema, is releasing The Hobbit: The Battle of the Five Armies on December 17th — which makes it a likely candidate.
But this news gets even better. The trailer is reportedly very “Batman heavy”.