Just the other day i was reading "Unfinished Tales of Númenor and the Middle Earth" (Portuguese version) and in about page 80, Hurín goes to the Nirnaeth Arnoediad, and just as he is ready to ride, he shouts:
Lacho calad! Drego Morn! (Flame on, light! Flee now, night!) something like that.
I think the "Lacho calad!" should do a great warcry for elven forces.