How big do you want to go? I had a Boston Terrier. They are smart and sweet and VERY energetic. And they are not all-day long barkers, but they are excellent watchdogs. We had someone who was installing a tub for us once, and Bonnie (I heard later) kept coming in to see what they were doing. It was like she was an inspector general. Everyone was at work, and she was sleeping in the overstuffed chair in the living room, when the mailman came. WOW! She jumped onto the register and began barking at the top of her lungs. They are very bright, small, and easy to care for - male or female.
