For me, the E3 2012 absolute winner was Watch_Dogs.
The aesthetic, the premise, the gameplay... it was a breath of fresh air (or if you don't want to go that far, something strictly "different") among so many fps titles and the standard flare we got.
I will admit that the first time I saw the teaser I didn't liked it very much, but when I got the context behind it I went back and absolutely loved it.
This is the result of it... and my now crescent expectation of this title.