Dark Knight - with the Joker popping up and Harvey Dent ads
The year leading up to TDK is some of the best viral marketing ever. They started off by revealing The Joker, and then sent fans on treasure hunts to find other items, they sent things like cakes to fans, you got to vote in the Gotham City District Attorney election, get recruited by the GPD, got papers for The Gotham Times (with fully written articles), websites galore, the GTV interviews, and then to top things off, the night before the movie dropped, all of the sites got hacked by The Joker, and you got a news update message saying that one of the banks in Gotham was being robbed.