What is your favorite ultimate ability for that class?

Here's the previous list as of version 2.1. Here's the list for version 3.0 (this takes into account not only the usefulness of the Special Ability, but also the usefulness of the means by which it can be obtained):

1. Warlocks (the Special Ability is good, and the skills for obtaining it are excellent)
2. Orcs (the Special Ability is excellent, although the upgrade uses a catapult, and I prefer a tent with a ballista)
3. Demons (everything is very good, but it's unclear why a demon needs a Pain Lord)
4. Elves (good Special Ability, with good upgrades leading to it)
5. Dwarves (magnificent Special Ability, however, the upgrades leading to it are awkward)
6. Necromancers (decent Special Ability, with good upgrades)
7. Humans (weak Special Ability, but good upgrades)
8. Mages (average Special Ability, below-average upgrades)