So far for me, it's been the Spencer/Roane Country area, where WVAngler (along with others) has made an effort to put out all different kinds of caches (hard ones, easy ones, earth cache, Wherigo, puzzles, the Black Walnut Trail, etc)
Then around Kenna and Ripley, jbgrug has put out a bunch of head scratchers, and the Taylors, 3good_geocachers, and several others have put out some good ones.
I still have a lot of places to go, though.