Yeah once. Didn't have to fire, however. I was working something near a home. When I started up a trail on next the property line, the homeowner let their rottie out of the house, and out of the yard. It came after me with a vengeance. I cleared and pointed. The hound apparently had been in those circumstances before, stopped about seven yards from me and we had a bit of stand off. I finally heard the homeowner, who I realized was standing inside the screen door, calling the fiend back. I suspected the owner had been watching all along hoping to see me become a chew toy.
On a training note, I had been using a Safariland thumb break top draw holster on my duty belt. During some handgun retention training, on of my compadres grabbed my holster and launched me in flight, bending the shank. I went shopping and bought a Safariland SSIII retention holster, but was unconfident in my ability to defeat all of the devices to draw the pistol under stress when qualifying at the range. For that reason, I'd been swapping the old thumb break back onto my belt on range days. That day on the trail confronting the dog, however, I had apparently stored enough of the required skills into my procedural memory because I was able to subsconsciously draw and present as fast as I ever could with no fumbling. Never went back to that top draw.