Back when I still liked animals I had a collie. It ate everything, including the fence. It ran away. But, it was a quiet well trained dog. I'd recommend that.
cairn terriers are not only cute, but they are better with being trained on a leash than any other breed of dog,bar none. Plus they are very very loyal and friendly. i miss my cairn. He was best friend for 15 years. No matter what mood I was in, he was always super excited to see me.
Shih Tzus pure or say cross with a Maltese? We have one and she's a definate character (and has grown up with a rottie so thinks she's a big dog too). Given her love of water we sometimes wonder if she's also part duck. The coat gets long and does need clipping but there's no shedding. The OP asked about JAck Russells but might not be a good choice - they need to be kept active or they get very destructive and one of the most common biters amongst the small breeds.
If you want a good protective watch dog get a doberman or a rottweiler! Then again I am partial because all 3 that I have had in my life were/are wonderful dogs. Loyal and they have a need and desire to please their masters. Playful too. Hollywood has made them out to be monsters but they are wonderful sweet dogs. You reap what you sew. Treat a dog badly you get a bad dog. Love and care for a dog and they will do the same for you. http://en.wikipedia.org/wiki/Rottweiler They also herd children Edit to add: Direct from WIKI In the hands of a responsible owner, a well trained and socialized Rottweiler can be a reliable, alert dog and a loving companion. Rottweilers that are well trained and cared for can be as well behaved as any other dog and, in general, quick to learn. The Rottweiler is a working dog that is also good for guard duties.
Because I can no longer resist behold the cuteness of the pom: Here's my current pup Marco contemplating his next prank Here's Coco who was an absolute angel.
My Shih Tzus are pure. I have two and they have extremely distinct and funny personalities. They LOVE to entertain, they are VERY smart and protective of one another. I also have four cats so they are tolerant of other animals. Personally, I have for most of my life been a cat-person. Since meeting these wonderful small dogs though, Shih Tzus will also ALWAYS be a part of my home. Both mine HATE water though--especially baths. One INSISTS on being carried when it's raining outside also. Funny, FUNNY creatures . . .
Black Labs are great dogs, but maybe not the greatest watch dogs. Border collies are very intelligent but require a lot of exercise and stimulation. We had one as a kid and she would herd us in the backyard - running around us in ever shrinking circles. Best dog I ever had