When John Stewart fills in for Hal Jordan as the Green Lantern.
John: The one week I fill in for Jordan, and it couldn't be some hairy-ass monster?
After Batman walks out the meeting with the League:
John: He's even friendlier than they say.
When Deadman is trying to get Batman to talk to Constantine, he possess his body and writes Constantine's name all over his room. Batman was not amused by that. When Deadman tries to possess Batman again, Batman is able to reject him out of his body.
Constantine allowing Batman to see Deadman because he doesn't want to play telephone between them.
Batman's reaction to Constantine and Zatanna entering one of the victim's mind and dealing with a monster made of feces is just "Hmmm". He pretty much says this throughout the movie.
Constantine is determined to work on the case of dark magic-induced homicides himself, completely repudiating Deadman's attempts to have him work with a team or even be their leader. However, he is open to having Zatanna's help. Zatanna agrees... so long as they all work together as a team. Constantine's response?
Upon meeting a group of Shades, they float around Batman and remark about how vexing he is for cheating them so often. The Shade gets right into Batman's face, who can't see them mind you, and after a moment Batman simply says "Boo." and actually scares the shade.
Felix Faust. The guy has literally no idea what's happening outside. From his perspective, he's just minding his own business, trying to reach a deeper understanding of magic in his observatory, when all of the sudden, a demon comes crashing down through the roof, followed by Zatanna, Deadman, John Constantine... and Batman.
A mix of fridge hilarious and Black Comedy: At the end, Richie is dragged of to hell by the shrouds. The heroes watch solemnly as he screams for help... Except for Batman, who can't see neither the shrouds nor Richie's soul. Meaning that he's just looking at an old guy that asked Constantine for help, and then just fell over. Boston's concise response to the whole spectacle is just tops it off though.