Lonic was banned with good reason, I'll tell you that.
...Anyway, whenever this topic comes up, the first names that come to me are penguinwizard and Roy Koopa. Penguinwizard has always stood out as a unique character in my mind, through his interests and the intelligent manner of his posts, among other things. And Roy Koopa had a lot of great insight on the Mario universe, as well as being the author of some really awesome fanfics.
Both of them have, since "leaving", come back briefly and posted a couple of times.
Go Moon!