I have a nice big Black Lab (45kg) loud as hell (we don't tell him off for barking at strangers)
Had a guy jump over the fence, I saw the dog just take off after him, guy looked up and and bailed back over the way he came losing a shoe to the dog and the guy was caught just around the corner.
I was standing in the kitchen and the look on the blokes face was priceless, I think he pooed a little...