Elfen-Kürisser (Civ4 FFH)
Elven Riders rely less on tight formations and finely crafted armor than on speed and agility. They put their lighter frames and natural grace to good use when battling other races Knights, though their honor is no less fierce. Loyal to their queen at all times, Elven Riders are the first choice to accompany any diplomatic envoy, times in which even they will engage in the pageantry that often accompanies their human counterparts.
High strength, high movement rate, and a decent withdrawal rate combine to form a strong utility unit. There is no best use for a Knight, it's the fact that they can do many things so well that make them so valuable. A civilization can only have 3 Knights at once.