When it comes to what stands out between Khall and other characters, I see a few things.
For one, Agnes will probably not be his favorite individual xD
She likes to "Jam" and generally be loud, from what I read. Not to mention the fact that she makes light. Poor Khall!

Then there's the real sound-maker. Aside from her power, I think Khall and Ellie could get along. Considering they're both not very popular there could be something. But Khall isn't the best at showing who he likes, usually. So maybe not.

When it comes to Michael, it's social anxiety vs. plain preference to do his own thing. Maybe they could hit it off, but then again maybe not. His personality, and his power, are nice and quiet, though. :3

As for Eli, I think Khall would somewhat admire his stubbornness, which they share, and his overall attitude. Eli having his own moral code is a big plus for the other, and his tendency to help others instead of hiding it behind a mask is also not a negative.

As for Jess, I think it almost splits even, maybe leaning towards the positive side. Her being happy/charismatic is something that's easy to follow, so that's a positive. And a sharp tongue usually comes with comedic side affects, and he does enjoy a good laugh. Not to mention...she can make rain! Which Khall loves.

That is all my thoughts at the top of my head, in terms of Khall + Someone else. >.>