What do you want to know? We train our dogs for "sport", but we have a few that are "civil" and, I have no question they would bite for real should the need arise. Owning a dog like that is no small undertaking. Even if you buy one "trained" be prepared to put in the work to maintain control. It's a big responsibility.
Mals, Dutchies and GSDs are the most common breeds, obviously, but the right dog (of any breed) can do it. My most "civil" dog is actually a Boxer. Our Dutchie is very equipment (sleeve, tug, suit, etc) focused and, if there is no equipment present, she is the sweetest girl. She is about 60/40 Prey-to-Defense. My Boxer is NOT equipment focused. At all. He's about 60/40 the other way (Defense-to-Prey). He's a big dufus around the house and loves people, but he is VERY serious (almost scary) when need be.