I know there is at least one example of a mob of an orc-type race that can't be enslaved (exiled orc shaman). Are there any other orc/ogre/kobold etc mobs like this or is that mob a unique case?

Or whatever that swamp is called. I want to say those orcs can't be enslaved at all. Lots of others can't be either. I think basically anything that is directly aggro (instead of a prog).