The only ones I can think of, both of them terribly precious to us, are Dave and Walker. Very blessedly, though an awful lot of others are quite old, (Earl Boen, Will Ryan, Corey Burton, etc) they're still alive. Still, it's sad to wonder how many will be alive in ten or twenty years.
As for post-hiatus, everyone's fav is Jay, but that's partially because he's funny. If he weren't so hilarious, poeple wouldn't love him nearly as much. So it has at least as much to do with that as with any real complexity or sympathy of his character.