Hi just wondering if anyone else has encountered this or knows what it is?
So I'm killing trains of zombies and every so often a puff of green dust will appear, it looks a lot like the dust from the phd flopper but obviously I'm not dropping from any height, also it's not the green mist from vulture aid.
Can any one help in identifying this?
It's the indicator that you've earned one of the many "perma-perks" built into the game. Examples of such are perma-Jug, Steel Barriers (harder to teardown or faster to rebuild, I don't remember which), perma-Deadshot, perma-Quick Revive, etc. Basically you get the affect of the perk without actually having to have purchased it. They last for awhile but they not actually permanent from what I understand.
It sounds like Deadshot. You get it for getting 2 headshots with 1 bullet. You can tell if you got it by all the zombies heads exploding when you kill them, even if you didn't shoot them in the head.