Standard scenario: I have just gotten my law degree and become a junior public defender. Too much crime; too many criminals walk the streets. I put on a 3 color costume and use the skills I picked up in college when I got my P.E. credit for curling. I am the Sweeper, keeping the streets of Nova Scotia safe from the criminal element.
And that's actually a bit more detailed than the average.
Now back in 1940 Jerry Siegel (nobody important, you might remember him as one of the guys who created some 3rd string guy called Superman) created The Spectre. It was brilliant. A ghost already has superpowers so using one as a hero just seems natural. It's far more convenient than having to manufacture some pseudo-scientific blarney like, "Drank a serum and jumped into a vat of creosote, giving you all the waterproofing powers of a railroad tie" as the source of the hero's powers and concept.
Ghosts are pretty super anyway, yeah?
|The Spectre..."borrowed" from Wikipedia|
The Spectre is cool, but he's gone through so many changes. While messing about with Spectre research I came across this guy:
|Mr. Justice! Seriously, what is going on in this picture? Those are, what, Alien Spider Monkeys? And that one is holding a tommy gun maybe? None of this happened in the issue, I assure you.|
He was in the bulk of Blue Ribbon Comics from MLJ comics and was in every issue of MLJ's Jackpot comics. If you can find these issues I highly recommend them both as great examples of Golden Age comics that are not DC or Charlton and for Mr. Justice.
All hail the ghost as superhero.