I really don't have a preference. Usually I don't make it that far into an episode but if I had to choose then Taking Liberties. "Lord weirdo" has a soothing voice. Ham radio is also good.
The worst one - the one episode that I loathe the very existence of - is The Matchmaker. I don't know who thought an eardrum piercing smoke alarm to kick off an episode was a good idea but I hope every night of their miserable existence was highlighted by a midnight jolt of loud noise. I may even go so far as to wish someone carelessly folded their new cashmere jacket as to misdirect the knap!