1. Families with 3 children under age 10 who think it's a great idea to get a Border Collie, then wonder why it nips the children.
2. People with little white fuzzy dogs (you pick the breed) who can't understand why the dog won't housetrain. (Could it be that it soiled its "den" for weeks at the pet store?)
3. People who keep asking, "How do I stop him from jumping up?" when the first thing they do when the dog jumps up is acknowledge him. (Off, down, shove, no, etc.)
4. People who tell me their dog won't come when called. How did they try to teach him? Ya, you guessed it - off leash, no food or toy upon return. Or, they punished him for not coming (I'd never want to come again either, if I got yelled at for doing it.)
5. People who want the dog to stop taking food from the counter (so, remind me, why was the meat left out on the counter in the first place?), but never listened to the lecture on how to prevent it - did they think their dog was the one dog that would never need to know?
6. Snobs who think their $1500 Somethingdoodle should be the smartest dog in class because they paid so much for it, or they imported it, etc. I love it when the little shelter dogs show them up

)
7. People who think I was kidding when I said each child in class needs to be supervised by one adult. Believe it or not, I had a woman with a hundred pound dog, and one child on the ground, one in her arms, who came without hubby and thought she was going to be able to do all the exercises. She had the kid in her arms the whole hour. WTH
8. The "but" owner who came to class, but each time you make a suggestion, it's "Muffy does it at home." or "Muffy doesn't like...", or "Muffy is very smart, I don't know why she doesn't like it here." (Could be that you never socialized Muffy off your lap, lady.)
9. The idiots who keep letting their adult dogs nose each other on leash in the lobby after you have told them "no contact" on leash. The famous "oh, she's friendly with other dogs" in yet another form.
10. There are more, but I'm sick of typing...