2. Green Lantern/The Flash
Hal Jordan and Barry Allen make up the comedic relief of the Justice League, acting as the team's more lighthearted, fun heroes. Together, they share witty banter and a nice friendship that would make for a great superhero buddy-cop film. This would not only expand the DCU a bit more, but show audiences that not all of their films will have the same darker tone as The Dark Knight trilogy or Man of Steel. The Flash and Green Lantern also have two distinctly different (but cinematically exciting) powers and abilities. The filmmakers could find interesting ways for the two to solve problems together and play off of the strengths of the other. In the current New 52 continuity, the two even worked together before the Justice League was formed. This would be a great way to either re-introduce or reboot Green Lantern, and act as the big screen debut of the Flash. A film for each character may not be needed before a full blown JLA film is underway, but perhaps a team-up would be a fun road to go down first?