Spectre Coming To Arrow?
With Matt Reeves' Constantine having already appeared in episodes of Arrow, it could be possible to see Emmett J. Scanlan's Jim Corrigan, aka The Spectre, which was featured in the cancelled NBC Constantine TV series.
EP Marc Guggenheim tweeted out the episode 5x13 title which is "Spectre of the Gun."
It should be noted the Spectre appearing in Arrow is pure speculation, but at one time a Spectre spinoff series was in development and appearances by the Spectre on Constantine gave the show high ratings, so we see there would be some benefit to using the character (plus Spectre is pretty awesome). It's a shame the Spectre was never allowed to develop on Constantine, so maybe we'll see more of the character on Arrow.
The Spectre is DC's Spirit of Vengeance and is a vastly powerful character. John Ostrander's run on The Spectre is one of my all-time fav's.