My favorite would have to be the Reach. The rocky landscape makes it fun to explore and sneak around and once the main quest is finished, launching a self-imposed campaign to purge the Forsworn is always fun.
I guess my least favorite would be Winterhold if only because it's out of the way and the college was a bit underwhelming.
I guess my least favorite would be Winterhold if only because it's out of the way and the college was a bit underwhelming.