What is your favorite ultimate ability for that class?

Elves have a very good ultimate ability, but I don't like many of the skills you need to take for it. I'm especially annoyed that you have to take "Permanent Luck." Because of this, "True Luck" becomes a little worse. There are also many other unpleasant things...
Mages have a very useful ultimate ability in itself + very useful skills that are needed to learn it + after it is learned, no magical schools are needed at all => a lot of space is freed up for other useful skills. Result: winner :)
Necromancers also have a very good ultimate ability, but it is not entirely universal (it won't save you against another necromancer :) ).