It's always interesting when a big name hero has one of their main villains cross paths with a different hero. Which swaps have you enjoyed in the past, and which would you like to see?
I'd be interested in seeing stories about:
Green Arrow vs. Black Manta
Green Lantern vs. Scarecrow
Batman vs. The Flash's Rogues
Superman vs. Reverse Flash/Zoom
Martian Manhunter vs. Gorilla Grodd (got a tease of this in "Justice" by Alex Ross)
Wonder Woman vs. Ra's Al Ghul (more than that swordfight)
Hawkman & Girl vs. Black Adam (more than that fight)
Captain Marvel vs. Ares
Aquaman vs. Vandal Savage
Zatanna/Canary/Vixen/The Atom vs. Sinestro
I like the first match-up because there's good potential for philosophical searching. Both characters center their mission on combating oppression, but Manta recreates it while Ollie seeks to combat it. How far is too far? Is Ollie sympathetic at all to Manta's motivations? Could Manta challenge Ollie's qualification to judge him? Some people may not like that kind of story, but I think both characters are political enough that it would do them justice.
The second one is interesting because it pits a Green Lantern against fear, but in a different context. And one thing I haven't seen is a ring wearer having their mind affected, and that manifesting itself in the constructs
Batman vs The Flash's rogues would be cool, because while Batman is used to dealing with organized and often high-powered street level criminals, his often leave a trace or a calling card out of hubris, and operate in his comfort zone. Here he'd be facing an organized group without the gimmicks and the lofty aspirations, led by someone just as cool-headed and methodical as he is.
Superman vs. Reverse Flash/Zoom would be great. The former because I would be really interested in seeing Thawne try to time travel and prevent him from becoming Superman, creating a type of Flashpoint story in which Clark reflects on what good a childhood and upbringing he had. Zoom would also be interesting because he wants to cause tragedy to make heroes better, and Superman, like I feel the Flash is supposed to be, is the epitome of good without traumatizing tragedy (discounting the removed loss of his home world). And in each one, there's an element of just not being good enough that Superman would have to overcome. Whether its raw speed like Thawne, or the split-second time travel of Zolomon, Superman would be a step behind in combat and in saving those in danger. He'd have to find away around that and be clever & creative with his powers.
MM vs. Grodd has obvious intrigue, because they are both telepaths. But there is more to explore there, such as the fact neither is human, and the fact Grodd belonged to an advanced civilization that perhaps reminds J'onn of Mars. And of course, J'onn would likely see the white martians or Ma'alefa'ak in Grodd's greed and hunger for power.
WW vs. Ra's is cool, because each of the civilizations they represent are kind of juxtaposed, mirrored but contrary. The league of assassins is meant to purify decadent and corrupt human populations, while Themyscira is a retreated paradise. One of them plagues humanity when it is in crisis, but the other gave rise to a heroin who took a risk to lend man's world a hand. Each is also tied to history and war in a unique way.
The Hawks vs. Adam is great because of the mystic and Egyptian themes that they share. They're also just baddass. I'd love to see a chapter in history that intertwines their past that parallels a conflict they have in the present. Some interesting personal interactions there. Hawkman hates tyrants, but wasn't he simply a benevolent one in his origin?
Captain Marvel vs. Ares would allow him to really interact with the realm from which he derives his powers. Perhaps the gods are jealous of his tap into their abilities; the Greek gods were often jealous, and maybe Adam exploits that.
Aquaman vs. Vandal Savage is cool for a few reasons. They're both very masculine characters (nothing like a chest-beating brawl), and both have experience as leaders of nations and armies. It would be interesting to see Savage make a play for Atlantis; he's not Orm, it wouldn't be a coup from within, but something more sophisticated. Maybe he gets an army somehow? And how does his immortality complicate Aquaman's apprehension of him? Does he bring him back to the surface dwellers (where he may escape again), or does he try Atlantis, where his people might fear his presence?
I needed to include Sinestro here and wanted to use someone different, but I couldn't choose. But I think a team dynamic would work great, since Sinestro is pretty powerful. I think the Atom is an important element here as Sinestro is so haughty that he'd never consider something so small a threat.