Least favourite are the ones on the uphill sections of my commute!

I hit a scottish terrier once - it darted out in front of me and I was braking and trying to turn as I hit it. I went over the handlebars and messed up my shoulder. The dog owner was upset at me (she felt that I shouldn't be going that fast)- which made me wish that I had hurt the dog - I was definitely more injured than the damn brick-dog.