My co-worker got an Australian Sheepdog. A BIG one! He's raised dogs his whole life, but went for professional training because that dog is likely smarter than he is, lolz!
An absolutely beautiful dog! He wouldn't hurt a fly... unless you trespass in his yard or threaten his owner or doggy-pals. He's a trained attack dog.
He'll lay in the open gateway & not go past it, just watches everyone and everything!

One story he tells is he was walking "Aussie" and another (bigger than Aussie) dog being walked broke away and ran at them. Aussie just "hunkered down" and that dog nearly pissed himself stopping & running away! Yelping and crying. The other owner was mad but he said "keep him under control or Aussie will take care of him". Never had that problem from that guy again :>