Touma Kamijou
The guy doesn't like magic, and he's kind of closed off and aloof, so Zelgadis really shouldn't like him. But... as a fellow aloof person, Zelgadis actually does like the guy. He's honest and seems to have a "whatever" attitude about things, which is just the sort of quasi-nihilism that Zelgadis himself practices. He likes having someone to chitchat with who doesn't really pry and doesn't want to get too personal.
Shipping potential: Nah. They could be buds, if both sides put in the effort, but who knows if they'll bother.