During a discussion with a friend of mine concerning DC and Marvel movies, our discussion turned to both the upcoming Justice League movie, and the Marvel Cinematic Universe, and the world building thereof. Said friend and I wondered what cameos at world building would occur, if any. This eventually lead to what cameos we'd like to see. Due to my personal interest, I turned to the largest commodity of comic book... experts... Around. So here's the scenario:
The Justice League movie is coming up, but no information has been released yet. We'll go with the classic (to me) Justice League line-up for the film: Superman, Batman, Wonder Woman, Flash, Green Lantern (Hal Jordan), Aquaman, and Martian Manhunter. Now how they come together in the film is up to you (within reason, no slash fic kinda stuff, things you could reasonably see in a Justice League movie), but the key here is what cameos you'd like to see in the film, i.e, what hints at a larger DC universe. Can be as minor a character as you like, hero, villain, either/or. The trick is the cameo has to be relatively subtle, meaning something a fan would pick up on that doesn't distract from the theoretical plot. I'll provide some of my examples:
Say I wanted a cameo for Hawkman/Hawkgirl. In the Justice League movie I see, Darkseid comes down with his parademon army. Say the initial invasion lands in Egypt, where Batman finds some bloodied feathers around a pair of parademons that (using his analytical skills) he determines were beaten to death with a mace of some kind.
Say I wanted a cameo for Nightwing. I could see Superman coming to Batman for a team up, trying to get him to join a team he's putting together. Say while trying to convince him, Superman says something along the lines of: "I heard you used to run with a partner. This wouldn't be too different." To which Batman could reply: "Things didn't work out. I work solo."
Stuff like that. Things on the level of Marvel's world building stuff, where they'd put in subtle hints of other characters, such as a hint at Wakanda in Iron Man 2. So: Your ideal cameos! Go!
(I apologize if I'm not making this clear enough, or if I'm rambling. If you have any questions, ask, and I'll do my best to clarify any misunderstanding.)