[Yrkoon]

If you include blessable unit in your pool of units to choose from, then I'd say blessable non-capitol only units are the best.
Being non capitol only they can be recruited in large numbers, and being blessable they can be made much much powerful than regular units. Sure, one tarrasque will eat one blessable unit for breakfast. But armies of units can be easily raised, and they will mop the floor with the tarrasque (or any very very strong expensive unit)