I don't know if you would call it a grunt or a growl but I never knew rabbits would do that. (Or a scream for that matter. What a horrible sound.) The first time I heard Clovie growl it really scared me and he usually accompanies his growls with a lunge as if he were going to attack. Or he may scratch at me with his front paws. I learned early on that you don't want to go near the crock when he's eating his pellets. That's serious. And he doesn't like it when I reach for him head on. Better to approach from the side.
Another thing that he really doesn't like is when you "walk" your fingers toward him. Must be pretty scary. My daughter's finger ended up in the gap between his front teeth and the molars when she did that. No harm done but lesson learned.