One of the things I hated during a festivity in the Rift:
Fight 4 brawlers while being surrounded by neutral people (white outline).
Accidently attacked someone else and it's a bounty for me!
(good thing I needed to log out anyway. Time solved bounty for free)
So yeah, an option to disable "friendly fire" would be nice. You'd have to turn it on again when you want some bait or rob / kill a guy, but it has my vote.
Used to be awesome in PvP when there were deer in cyrodiil.
Used to be able to take cover in a herd of deer, and also use them for healing with the 9% regen all stats on death on the soul magic dot