What's up Zonker?
I'm hearin' ya on the argument that Adams/O'Neil team were the catalyst for the Bronze Age. Adams started working at DC in the middle of the Silver Age, and up until about late 1968 his work was constrained to fit the mold of the books of the time, but really, starting with his work on Strange Adventures, he began breaking the mold and doing his own, revolutionary thing. Both Deadman and Batman became what could be classified as anti-hero, darker characters that seem to be the concensus on this thread of what the Bronze Age was about.
Neal Adams also changed the way the industry worked behind-the-scenes - both in advocating creators/artists rights and in the way the books were made (specifically, the printing/coloring process DC started using). He was a revolutionary at the start of the revolution. In addition, Adams' influence resulted in changing the popluar artistic style from cartoonish (Kirby, Ditko) to the more photo-realisistic/highly detailed style seen throughout the Bronze Age (Smith, Byrne, Perez...).
I'm afraid though, that Detective 395 is too much of a stand-alone book to qualify. On the other hand, GL 76 is a recognized Key that was the beginning of a solid 2-year run by the Dynamic Duo. A DC book, GL 76, is also supported by the fact that DC starting putting out the anti-hero, darker, horror themed, non-superhero characters, monster-centered books a good year or two before Marvel FOLLOWED suit.
In a nutshell, it looks like we're down to GL 76 (great choice), Conan 1 (solid choice), or Giant Size X-men 1 (whatever!!). Who's gonna start a new thread with a Poll?