Batgirl / Black Bat / Orphan (Cassandra Cain)

First appearance (of an unnamed Cassandra Cain):
Batman #567 (July 1999)

NOTE: I'm not sure if the "Batgirl" on the cover is suppose to represent Cassandra Cain or not, since at that point in time Huntress (Helena Bertinelli) was still wearing the Batgirl outfit. (In fact, the story features a few pages of a Batgirl in a graveyard before getting to Cassandra Cain, but again I'm assuming that one is still Helena Bertinelli).

And a few pages into that issue:







Still later in that issue, Cassandra is able to communicate to Barbara Gordon and others that she is the daughter of David Cain (the man with the rifle).
And in Batman: Legends of the Dark Knight #120 (August 1999), Cassandra will be given the Batgirl outfit that Huntress had previously been wearing.

From Batman: No Man's Land Secret Files #1 (December 1999),