I've been toying with Gunslinger. It is a very neat skill. One way to make it even better is to add "auto release" once you've selected 5 or 10 targets (depending on your rune). It will help out so much because it is really hard to count if I have selected up to max targets or not during the heat of battle. That way we just need to select and then the gun releases on its own, or we can let go the button to shoot if we only want to shoot a few targets.

I am trying to maximize Friendly Fire. Still not sure if this rune is working or not.