Batman is Bruce Wayne's primary and most famous alter ego, but he has at various points taken on other identities. Can we name them all?
Off bat (hah), there's Matches Malone, the Batman of Zur En Arrh, and -- I suppose all the versions of himself he took on in Return of Bruce Wayne (Caveman, Pirate, etc).
What others?
(Let's NOT count alternate universe Batmans/Bruce Waynes, otherwise this will be endless. )