Don't forget the Border Collie. Only slightly larger than a beagle, extremely smart and very loving. They love to run and play. My Muffin was an excellent watch dog and only once showed any aggression and at the time it was the correct response. Normally she would just bark at trespassers but one night while my wife, daughter and I were sitting in the living room watching TV a strange young man leapt over the balcony railing and tried to crash through our sliding glass door. Muffin was on her feet in a instant and launched herself through the air directly at the man. Fortunately, the glass held and both man and dog bounced off, unhurt. Upon seeing the dog the man jumped back over the railing and disappeared.