5. Alan Scott
Checkmate would be a great addition to the DC Cinematic Universe as a counterpart to the Marvel Cinematic Universe organisation S.H.I.E.L.D. They could deal with abnormal situations, such as those involving Superman and Batman, in the same way S.H.I.E.L.D. have dealt with the situations involving Thor, Iron Man and Hulk et al and would, therefore be very easy to introduce in a movie. One man who has been very high up in the Checkmate organisation in the comic books is Gotham City resident Alan Scott (think Nick Fury or the upcoming Robert Redford character Alexander Pierce in terms of comparative positions of authority) and to have him appear in such a role could be an interesting little point of potential future development. For those who don't know, Alan Scott is a veteran Green Lantern whose ring is not the same as the standard Green Lantern ring. It is magically powered, instead of the alien technology that powers the rings worn by guys like Hal Jordan. As a result, Scott tends to deal with more supernatural threats than other Green Lanterns and has associations with groups like the Sentinels of Magic, so his inclusion in the DC Cinematic Universe could serve as a link to movies involving characters like Madame Xanadu, John Constantine, Zatanna and Doctor Fate (which would be amazing in live action).