Like Claude, I would have quite a long list of those charactors I'd like to see do a repeat. But here is my "short" list.

Ricky from "Ricky"

The fiesty Mother Superior from "Sanctuary"

The rock singer from "Metamorphasis"

The blind Laurie from "Prometheus"

Anyone else who positively knew that David was the Hulk, and he trusted to keep his secret.
This last one, it would seem to me, would make for very interesting scenarios, as these would be folks
that David could relax with for a time, and they in turn, would know that the Hulk would not harm them.