ManOfMiracles
Hogwarts Class of '86
I've found their fort-building useful if there is a powerful civ next to me across an isthmus. Plant stacks of crusaders there and let them build their little forts (without wasting my workers' time) to keep the enemy out until I have cavalry and can go pound on them. Then the crusaders are used as the first defenders in the cities I take until I can get infantry.