Chinese Shar Pei
To be honest, when most people see a Shar-Pei they probably don't think of an overly protective or even especially effective guard dog.
After all, the thing kinda looks like a honey cruller thanks to all those rolls. In fact, it has so many rolls it could open its own Swiss bakery.
In all seriousness, we could sit here and burn this breed on its appearance all day – but that's not what you're here for.
The Shar-Pei breed is known for being devoted and loyal to its family and people it knows. This probably explains why the Shar-Pei was used as a palace guard in China.
All those wrinkles we were making fun of earlier, well, they are intentional because the extra skin allows this breed to turn and bite anyone or anything that grabs them from behind.
Naturally predisposed to being territorial and aggressive, the Shar-Pei's true protective side comes out when strangers come near whoever or whatever it considers as its own.
For this reason, Shar-Pei owners are advised to socialize their dogs from a very early age to lessen aggressive behavior and barking.