Mods:
Plane Sailing - very cool; has an endless array of examples from in-campaign play.
Umbran - very cool; able to readily see both sides of an issue.
Hyp - I just have to know if he has all this encyclopedic knowledge in his brain, or if he checks books with lightning speed.

Oh, and very cool.
(I only really ever interact with rules forum mods, so this list is probably biased.)
Nonmods:
Any of my players - out of general curiosity. Out of fairness, they have to top this list.
Rules forum regulars - though we argue, I suspect we have much in common.
javcs - has fun and wacky ideas.
werk - very cool in a discussion.
sukael - thinks of amusing ways to break the universe.
Jemal - shares my sensibilities on what is and is not powerful (most notably on AC.) I'd be wary if we met on opposite sides of the DM screen, though.
CanadienneBacon - a gamer open about her faith online is a rarity.
shilsen - I have to see what he's like in person.
. . . this list is going to wind up being ridiculously long. :\