For myself, the best one had to be Bondari and his party. I recognised those fresh party types, and I've seen that kind of thing happen in PnP roleplaying (especially the bickering, and thepicking on the low level wizard "But I heal you guys!"
A few other favourites of mine would be the Spectator Beholder (everyone loves him right?), the bickering between Jaheira, Aerie and Vicionia (if you're male), and the interaction between Jaheira and Haer'Dalis if you go to the Promenade.
Great stuff