Mushishi episode 12 was incredibly awesome. I still can't get over how beautiful and striking this anime is. The animation is absolutely gorgeous and I am in love with the end theme.
The Ginko and Toroyami Mushis were some of the coolest. I am so making a sig with those two in them. This was one of the best episodes. It explained alot of questions about Ginko.
Edit: Nui's VA also does the narration! She was also Queen Serenity in Sailor Moon and Megumi Takani in Kenshin. She seems to have done alot of minor roles in zillions of anime (and was in the Japanese version of Kingdom Hearts).
Ginko's VA is almost the opposite. Mushishi is only the second thing he's ever been in, and the only one where he has a large role.