For me, the choice is easy and while it’s not on the CBR finalist list, it happened in the pages of Batman #600 (but not in the issue's story) and smacked me square in the face. It was a house advert for an upcoming mini-series and it featured this piece of art;
Forget the words around it, this picture said it all. DC was finally bringing back the 'Big Gun' Justice League. Aquaman, Flash, Batman, Wonder Woman, Martian Manhunter, Superman and Green Lantern all in the one book. Even Mark Waid’s plot was irrelevant – if the League was reforming I was going to be there – right after I finished ‘wowing’ over that ad.
So that's mine done - what was yours?