Pet Peeve: "Tough dog" syndrome, or put otherwise, people in populated areas who keep unfriendly dogs. One thing that's popular in some of the rougher Philly 'burbs is Rottweilers and Pitbulls, which serve no purpose other than terrifying friendly neighbors and occasionally mauling a woman or child. And sadly, we see quite a bit of that every year.
You always hear from these owners that it's a "guard dog", which is just stupid. Their brain must be even smaller than their tiny phallus, if they honestly believe any dog (even a Pitbull) is going to stop a full-grown man intending to invade your home. I can stop even the toughest dog in about 2 seconds flat, with a short baseball bat or a 3-foot length of 2x4, so who are we kidding here? If any invader to your home is so badly armed that they cannot handle a dog, then they were never a real danger to you, anyway.
A watch dog is a useful thing, letting you know when trouble is near. But a "guard" dog isn't really guarding you against anything more than your neighbor's 12-year old kid. Our tiny but noisy watch dog is more vigilant than any Pitbull or Rottweiler, she'll let me know if a gnat farts 100 yards away, but she's also kid-safe. She lets us know when anyone is about, which is all I need, as I'm better armed than any dog.
When I was a kid, my parents owned a lab/shepherd mix, which we used to joke was so friendly that she'd just lick any intruder to death. Then one night someone tried breaking into the house, and that dog went full-hostile mode, in a way that really surprised all of us. Dogs are smart, even the normally-friendly ones.