Perhaps no other artists defined the look of Batman in the Bronze-Age as Jim Aparo. This is the blue and grey suit most people of my generation think about when they think about their childhood impressions/recollections of the Dark Knight (see his cover art drawing above).
With the heavily shadowed face, the batwing-like cape, and big bright yellow utility belt, Aparo took the 1960s Batman (still mired in schtick), and made him more formidable ~ more of a creature of the night. Batman's appearances in daylight would become a thing of the past, his relationship with the Gotham police would grow more mysterious, and he would become more truly the ambiguous hunted vigilante our younger generation knows him to be.
I'll be posting a lot of other variations on the Dark Knight's costume in the months to come, and adding this plate to the Batman Gallery once I've got Robin's traditional Bronze-Age costume ready to go as well.