I've swung at many a dog with my frame pump. I only connected a couple of times, and only once hard enough to bend the pump. Generally, yelling and swinging anything is enough deterrent. I'd never stop to yell/wave my arms. Too much chance of another dog circling from behind. Or having to answer Farmer John's questions at the pointy end of a 12ga as to why you sprayed/hit/antagonized his dog. Most people do not take kindly to their dog getting sprayed even if the dog was in the wrong. Most dogs are just protecting the turf/territory in front of the farm, so the quicker you exit the area, the better off for everyone. Adrenaline is your friend!!! As they say elsewhere on BF - HTFU!!

My college cycling club had at least one dog as a 'kill' to its credit. One little yapper raced out to the road and was so fixated on the ride leader that it literally got ran over by the paceline (twisting a few bikes in the process) Try to explain that to Farmer John...

I had one incident on the way home from the tennis courts one night while I was still in High School. I was carrying the tennis racquet across my handlebars and this dog came out the shadows. One swift instinctual reaction backstroke with the edge of the racquet and there was one piled-up dog on the side of the road... Worse was the fact that I knew whose dog it was. They thought that it had gotten hit by a car...