Tal Celes and Billy, as well as Harren and, um...himself.
In a somewhat more serious vein, I really admired the Neelix-Tuvok relationship, Despites all the slights and irritations on both sides, Tuvok came to attain a palpable level of respect and understanding for Neelix, ultimately in all of the latter's qualities, and who would have ever believed that would happen?
I liked the relationship between B'Elanna and Kim, especially early on, when his name was Starfleet. There was a true friendship and respect between them, though she certainly wasn't above ribbing him about his affaires d'amour!!!!
Tuvok and Chakotay certainly had a marked evolution in how they dealt with each other. Naturally, it took quite a while for the embarrassment/resentment to wear of for Chakotay, given how he came to know Tuvok in the first place. I always thought it fascinating when he was so dismissive of Tuvok, almost to the point of contempt. However, like all the Maquis-Starfleet elements that introduced any distinctiveness between the two groups, it faded away, and while I wouldn't say that they became close, the relationship took on the regular dimensions one would expect between two members of the command staff that perforce, had to work closely together.
I think that there would have been real potential in Voyager's regular, non-divergent timeline (however one might come to define that) for a truly satisfying, fulfilling, and passionate romance between Kes and Tom, if the timing had been different. He thought her beautiful, kind, humorous, and extraordinarily gifted, but he wasn't intimidated by any of that, as was the case with Neelix, during significant segments of their still important relationship. For Kes, Tom was responsible, dependable, had an engaging lightness of spirit, and represented all the hallmarks of a true friend. I think, over time, he also would be someone that would inspire great passion and ardor within her. But circumstances evolved that, after the breakup with Neelix, Kes became much more likely to find the fulfillment of these aspirations beyond Voyager, presaging her actual physical departure that would drop the curtain on the character soon enough.