It would help to know your living situation and how many people/animals live there. A dog that would be good for one person might not be good for a large or young family.

I like Cairn and Norwich Terriers. They are small without being tiny, don't need a lot of brushing but do need regular grooming, and are good guard dogs. But I don't know that they would be good with very small children and I know they need a firm hand. Also they are diggers.

What are you looking for in a dog?