Ned Brann

The original Dagger was an elusive, knife-throwing criminal. He concealed his true identity with a red hood, and committed crimes aided by a gang of similar looking red-hooded henchmen who also used knives. He only meets Batman once. He is erased from existence in Crisis on Infinite Earths.

David Rennington

The second Dagger was the owner of a blade manufacturing company called Rennington Steel. When facing hard times, Rennington starts masking himself as the Dagger, running an old-fashioned protection racket until being apprehended by Batman.

Dixon

The third Dagger appeared in the Batman and Robin Adventures, a comic series that took place in the Universe of the Batman animated series. This character's name was Dixon, a one time enforcer for a loan shark, who ended up in prison after a few run ins with Batman.

Powers and abilities

Skilled with throwing knives.