This is getting really funny.... Again, I have a parrot that will "alarm" me of certain circumstances and intrusions.... As for dogs.... MOST dogs with "guard" your home, because it's THEIR home too. They are, by nature, protective (to a point).
Again, I trained my boxer to become VERY well protective in all types of aspects, but dogs with small muzzels are not always the "prime" choice...but mine was extreme and put a hole in my dads palm at one point while we were training.
Don't even remember who started this post, and I don't know exactly why they need a guard dog... but if you are a family guy/gal with kids, then you need to watch what type of dog you get, and you need to know what you want from him/her. It can be a "scary" breed, or a mutt, but as through the ages, it shows, IF you treat your companion well, they will return the favor. I have seen a lot of cases, they do so regardless....
I can see from the post, you are not a trainer, so if you want a REAL GUARD DOG, trained in various forms, then....NO, don't ask here, go somewhere physical, speak to several trainers that specialize in this type of protection, find one you like, then GO with the trainer or investigate with the trainer on the type of dog you are looking for. After that, have the trainer test the dog, or several dogs and when one is found, work with that trainer side by side and get a postive result. I don't know what else to say or recommend. How high, by level, do you want this dog trained for protection?