I've been bitten by a Boston Terrier, a Dachsund, a Chihuaha, a Sharpee, two Rottweilers, a Labrador, and a Golden Retriever (the last two being my own dogs on accident).
None of them were serious, only one broke the skin (one of the Rottweilers). My worst 'bite' (several bites) was on a cat who wrapped itself around my right hand and went to town on it. And even that healed really well. No scars or anything and I was back at work the next day.
My sister, on the other hand, had a small part of her left ear removed by a dog. I don't remember the breed it was (happened when she was 9, I was 5) but it was a small dog like a Chihuaha or something.