Who's This? An acrobatic ghost.
How you could have heard of him: He's a member of Justice League Dark, not just in comics, but in an animated film (one of several appearances in animation, including his own DC Short).
Example story: DC Universe Holiday Special '09 (February 2010) "Unbearable Loss" by Scott Kolins
In this story, he trails Gotham City's hopeless. A homeless child, a woman contemplating suicide. That woman is the Scarecrow's mother. She didn't raise Jonathan Crane - her evil great-grandmother did - but when the villain kidnaps 13 children, she feels an unbearable guilt that makes her do something desperate:
So while the original concept of a ghost trying to solve his own murder (like an extreme version of D.O.A.) is a good hook (heh), once that story's done, Deadman remains a potent and likeable "street" hero, where most supernatural heroes function on a whole other level.
Who's Next? An assassin with a death wish.