This is hard, all of them are awesome. :3
Hm, maybe Milena and Christian. They're both Huffs, and since he had a Quidditch accident (I guess he was a part of Huffs Quidditch team) and is afraid of flying Milena might try to help him, not because she cares for others but because she's Huffs Quidditch Captain, and without Christian she'd end with an empty spot in team.
Or Esai and Darren. Esai would enjoy putting Darren back to Earth every time he shows arrogance (and since Esai can be quite arrogant, too, it could be vice versa). It would be interesting, with them being a social psychology stud and a lawyer, neither of them would end up without arguments. lol I don't see them as enemies though, more like two persons who spend some time in each other company, but can't say they trust each other?
Also, there's Meridian who'd jump into dangerous situation without thinking, so she'd most likely invite herself to go with Henry if she found out he decided to do something for the Order that might be dangerous, without taking no as an answer. If he tried to tell her she doesn't have enough experience Chang would only remind him he works in Department of International Games and Sports while she's an Azkaban guard (although suspended).
That's everything I can think of atm, let me know what you think! If you have any ideas feel free to write them.
Also, I saw the rant thread. Happy birthday! <3