I'll do anything I can to avoid a violent interaction with a dog, as it is never the dog's fault -- behind every "bad" dog is an irresponsible owner. Though I will happily call the authorities on the irresponsible owner.
I once got charged by a lab...I was riding along on a country road, past a house, and I heard or sensed something from my right. Looked over just in time to see a lab charging straight at me. Dog crashed into me, I swerved, made a somewhat-controlled dismount, and yelled my head off until the owner came out of the house to get his dog. Turned out that the dog had bent my outer chainring - frickin' Ultegra, so pretty solid. I told the owner that his dog must be injured, but we checked him out and he was fine. They have hard heads.
+1,000 on the retractable leashes. Anyone who knows anything about dogs - and training them - would never use one of those.