A hand made reasonably heavy earthenware pot has been my favourite. Made by someone who knew what they were doing, the lip of the spout is shaped like a rounded spade tip (by virtue of having the potter's thumb pull it out, I think); it doesn't drip, and if you warm it well first, keeps tea nice and hot.

I wouldn't think not washing the pot would be good, though: 'dark brown' indicates a buildup of tannin, which I think would be bitter.

I'm also tragically fond of a little two cup pink round ceramic pot I found at a flea market years ago. Has no maker's mark on it, so likely a very cheap pot when new, tragic because the glaze has crackled dreadfully inside, and that often leads to cracks occurring in the ceramic.