My least favorite ones are High Hall and Flames of Vengeance's Crow's Nest.
High Hall because despite the fact that it is the size, if not bigger, of Broken Valley's Hamlet, it literally has less than one-fifth of said Hamlet's NPC population.
Crow's Nest because everytime I'm there, I can't feel relaxed. I feel more relaxed hanging out in one of Ego Draconis's flying fortresses than in Crow's Nest, which of course says A LOT.
As for favorite... Broken Valley's Hamlet and the Battle Tower.
The Battle Tower as a favorite is obvious. It's your base of operations.
Broken Valley's Hamlet is an obvious choice too, but the one thing I wanna point out about it is the number of quests within it. Lots to do and many NPCs to socialize with.
What about you?