...it would be the nearest person, or the person easiest to hit in the general cloud of "assholes I want to kill". But you can totally make it more interesting than that. Instead, decide which user has 1. the strongest natural pheromones. This will generally be the biggest, strongest, most confident, and most successful user. If everyone's on Hither as well, I give up. 2. pheromones that would piss the smeller off most. Possibly related to sexual competition and threat analysis. So an alpha male, or even just a male in a heightened state of awareness because, y'know, fighting for his life and so on, would automatically be more threatened by the pheromones of a contending alpha male. Conversely, the BringIt enhanced pheromones of a female (or person of appropriate gender for the user to find attractive) might draw his attention more, possibly in concert with point #1, and since this is a life or death fight, this attention takes the form of bullets. It's your call to make as GM. And now, if you'll excuse me, I'm going to design rules for a pheromone drug that makes its victims inappropriately lustful.