There are probably a few threads I could have put this in, but I felt I should give it its own thread so it didn't encroach on others and can be replied to/ignored as people see fit.
I can't help but think perhaps a VSF outbreak of the "ghosts of mars" possession situation would be rather good for creating a very feral opponent for trained troops to take on.
Not only that but it could probably be imported into any historical, alternate historical, fantasy or scifi setting if you needed some reason for a mass of feral mostly melee orientated enemies.
I've just got an image in my head of the (rather over used I know) Battle of Rorke's Drift taking place on a terraformed mars with the possessed people taking the role of the Zulus.