Diana
A lot of people from our universe have already shown up. Me, Batman, Robin, Batgirl, Captain Boomerang, Green Arrow. And a few people from universes similar to ours; a few other Robins, a couple of Clarks.
And there are a lot of people from universes where our identities are common knowledge, so the civilian identity thing is much less of an issue now.
Lex Luthor and the Joker, among others, are also here.