Pets...
I currently have a dog, an australian shepherd. I would rather have a cat, but cats don't live long around here because of the lead-foot drivers in this area.
Australian shepherds are disturbingly smart. My dog was roaming and getting into stuff the neighbors didn't want him to get into, so I tried to train him to stay at home. And I THOUGHT it was working... until I started getting complaints again. Turns out my dog has figured out when I leave for w*rk in the morning I don't come back until late afternoon, so he has been doing his roaming in the middle of the day when I'm gone.
Party's over for him though. As soon as I found out about that I put a stop to it... partly because I don't want him causing trouble with the neighbors, but mostly because it hurts my pride to find my dog is smarter than I am.