5) Aquaman
Another recent Earth-2 Easter Egg in The Flash came from Jay Garrick when he mentioned that he’d paid a visit to Atlantis. That’s obviously a nod to Aquaman, and it gives Legends of Tomorrow a unique opportunity to visit that iconic location and hopefully introduce a small screen take on the character.
With Jason Momoa playing the King of Atlantis in Batman V Superman: Dawn of Justice, you may think that limits the chances of this happening, but not if the show goes in a vastly different direction with how they handle his personality and appearance (which should be easy enough as this version hails from Earth-2).
As a one off appearance, this could work perfectly.