Hmm, from the early days I'd say even something as simple as Locke's confrontation with the first thieves' guild member. It just set the tone for how the character would go, aswell as the players. Infact aside from the combat heavy end of the fsecond session, I recall it beign a great introduction.
The whole confrontation with Elric after the murder of the the innkeeper's wife (and the speech with the innkeeper afterwards, and the diplomacy with his wife).
The whole Goblin Hulk plan (including some evil double crossing and the introduction of King Balgrum)
The whole negotiation with the lizard men to stop them.
The epic ending of the thieves' guild I seem to recall was good.
The dinner party.
Gah, there's so many big and small moments, I can't remember a fraction of them!
I only recall the older stuff a little better because I've listened to those a couple of times each.