[Jennifer]

Many breeds of dogs both large and small have a natural tendency to be protective of their home and family more so than the Beagle. Many small terriers will ward off strangers with a ferocious warning bark.

It depends on whether you truly want a dog to be protective or just a deterrent. Personally I'd want a dog to be just a deterrent so rather a "watch dog" than a "guard dog". A personal favourite of mine is the Rhodesian Ridgeback. They not only come from the same group as the Beagle (hound group) but they make excellent family pets. They are large though.

 

[Jennifer]

I know several people who have Ridgebacks and smaller dogs and they get along fine. Ridgebacks are big but gentle like labs. I wouldn't recommend a Boxer as they can be extremely boisterous and are generally harder to train and a bit like Beagles in that they are eternal puppies...but that's just my personal opinions.