So, as the title says, I'm looking for the best undead to make use of a cleric's abilities in its unlife. What do you think is the best choice of undead for this?
If you read the flavor text for the huecuva down at the bottom, it seems to fit the title of your thread pretty well.
Specifically "While most huecuvas arise when a god rejects a heretic priest's soul, forcing the slain to rise as horrible undead, a huecuva can also be created with create undead... The spell can be used to create a huecuva using the body of a nonevil cleric... Creating a huecuva in this way is considered to be one of the most heinous things that can be done to a cleric that has passed away."
Well, that answers that. Rather quickly and concisely. Hats off to you, Nargemn. TIME FOR SOME ATROCITIES.