Not only warcries!
It would be cool to have "greeting sentences": concise sentences, uttered by the speakers, you would hear on meeting a group on the map.
You know how in the native version (at least, a few versions ago) when you met, say, pirates, they would say "Your money... or your life!"?
The text you read in the dialog box was different (quite longer and more detailed), but that quick spoken sentence you heard gave away the general sense of the situation in a very immediate way. Plus, it gave a thrill (especially when they catched you and you hoped otherwise).
I liked it.
For example, we could hear sentences like...
as an orc meeting:
- fellow orcs:
"What, maggot?" "What?" "You still around?"
- enemy men
"Now you pay for your deeds!" "Away from our Land!" "Foul creatures!" "Gondor (Rohan) shall prevail!" ... others?
- enemy men supply/prisoner trains (and agents)
"Back off!" "Back off, monster!"
- elves:
"This is where it ends", "<usual incomprehensible elven gibberish>" ... others?
- farmers:
"Mercy!" (by the way farmers should sound more terrified and less bold and aggressive in the dialog text as well)
as a free man meeting:
- allied armed group:
"Hail!", "Greetings!", "Hooo! <or however you spell the sound you make to stop your horse, this for mounted allies>"
- elves
"Dawn will come again", "<other elven gibberish>"
- orks:
"Pray for death!", "I'll feast on your bones!", "Submit to Mordor!" (to Saruman), "We are the doom of men!" "Men are weak!" "Man meat! Good!"
"I'll drink your blood!", "You are all doomed!" (probably this is too many variants already)
- orks supply/prisoner trains (and agents)
"Back off, rat!"
Just attempts, better sentences (and more specific to every faction or sub-faction) can surely be found.
The important thing is that they are very short (otherwise they quickly sound too repetitive) and communicate the situation effectively.
Ideally, sentences for hostile encounters should have more variants, as you are going to hear them a lot more often.
Admittedly this is a multiplication of the "voice needed" effort. Possible to do?