Favorite Voice Performance?

It's hard to pick one but I'll go with Negaduck. While similar to Darkwing's voice, for obvious reasons, the differences in personality between the two characters are clearly demonstrated.

I also really like his performance in Road to El Dorado as Cortes, a similar villainous voice.

His voice as Robotnik in Sonic SATAM is really great too.

I used to play World of Warcraft. The Mists of Pandaria expansion was one of the best. In that expansion Jim Cummings voiced a character called Lorewalker Cho. He imbued this character with a very wise, scholarly sounding voice.
Some people criticized him for doing a generic stereotypical Asian accent, but that was a bit of a silly complaint
Given that the character in question belonged to a fictional species of anthropomorphic panda-esque people who all had similar accents. In fantasy and science fiction media, it's not terribly uncommon to base aspects of culture on real world cultures. It would most likely have been cost-prohibitive to find and cast numerous Chinese actors for the various roles.