There's a scene at the end of Kill Bill Vol. 2 where David Carradine talks about how Superman's 'secret identity' is reversed compared to other superheroes, since he was born Superman/Kal-El, and adopted the Clark Kent persona as a disguise.
The character's claim is that no other character has their superhero and civilian identities this way round, but one could contest that Batman does (among many others, it's not as good a speech as you remember).
From the moment Bruce Wayne's parents were killed, he became Batman, and the playboy facade he presents to the public, is just that, a facade. Without being Batman, Bruce is nothing, an idea that's been toyed with many times in the comics, much to the dismay of Alfred. But there have been others who've tried to fill the cowl, either in Bruce's absence, as an attempt to surpass him, or just to help out in a pinch, some more convincingly than other.
Obviously Bruce is the O.G. (Original Gothamite), with Dick and Azrael having famously jumped in, but let's see which more surprising characters have donned the cape and cowl in the past.
In 2013, DC started their first line-wide crossover since the New 52 reboot, called Forever Evil. It focused on the villains of the DC Universe, as well as the result of Crime Syndicate travelling over to Earth-0 during the events of Trinity War. Many villains are empowered in the event, with one spin-off miniseries entitled Arkham War, focusing on Batman's villains.
Arkham War involves Bane freeing inmates of Blackgate prison, including the frozen Talons of the Court of Owls who had been stored there, to wage war against the Arkham inmates who are planning to divide Gotham up between themselves.
During the war, Penguin tells Bane that the other villains do not fear him, as he doesn't use fear in the same way that Batman did. Realising the utility of fear, Bane goes down to the workshop basement of Blackgate, and constructs a simulacrum of Batman's armour, in order to imitate him in the real Batman's absence.
He even begins to save the citizens of Gotham from the Arkham inmates, and renames Wayne Tower as Bane Tower, obviously. But eventually, Bruce returns, and reasserts his place as the rightful Batman of Gotham.