Try a Scotty. Beleive it or not, they actually have a more powerful bite than a pit-bull. In fact, a breeder that I talked to at the Scottish Games in Liganier, PA, said that they have the most powerful jaws of any dog, period.
Can you imagine breaking into someone's house, hearing that annoying high-pitched bark, and then having your ankle ripped off?
Seriously, if you want a decent guard-dog, but don't want a sheperd, try a coon-hound, they're dumb, but trainable.
If you've got kids, a Border Collie is the best possible breed of dog to get. They have TONS of energy, so they'll tire the kid out, and keep em quiet at night, and they're VERY protective without being aggressive. I have personally watched a BC keep a VERY determined 3yr-old from running out into heavy traffic. Terrific herding instincts.