My family owns a German Shepherd, and I gotta say, I love her. Highly intelligent for a dog, and also very loyal. I took about a month to housetrain her fully, and she learns very fast and doesn't forget anything. She's also very calm, and barely barks or begs for attention, and can be content with just being on her own. She's basically a huge teddy bear to people that she's familiar with, but with strangers and other dogs, she becomes very protective and openly hostile to the intruder until she's reassured that they're not a threat to her family. Very observant and alert to every threatening bird or leaf that dares to pass the house. It's easy to see why Shepherds are used as guard dogs, because she's pure strength on four legs that could probably kill someone if they were a big enough threat. While she doesn't bark much, when she does, it's loud and deep and has scared quite a few mailmen away from the house

She can be pretty goofy and eccentric at times, too. Almost like a cat, but 50 pounds bigger. She's great with kids, too. A perfect family dog, in my opinion, and definitely makes your house feel more safe, haha

It could be a good breed for NT's as well, because of their intelligence and loyalty. Maybe a better fit for xNTJs, but I'm an INTP and I love German Shepherds, so I guess it really all depends on what one is looking for in a dog.
