Wikipedia definition of Fanning
Fanning is a revolver shooting technique in which one hand holds the trigger and the other hits the hammer repeatedly. This turns the cylinder and hits the firing pin, in that order, allowing for 'semi-automatic fire' of single action revolvers.
I imagine this is probably in a merit, or something, somewhere, does someone know where? I also suspect this has not yet been ported to 2.0 rules, but would appreciate knowing if it has.