Haste

[Ewierl]

Meglobob said:
Cavalry or any other units with lances will benefit from haste as well. Alot of cavalry can nearly charge across most of the battlefield, with haste they can charge across all the battlefield. Inflicting alot of quick damage.

I also find it occasionally useful for fortress-storming; it can help your troops rush through the narrow gates first and avoid a bottleneck.