While not a domestic dog I remember tales of 3-4 Illyrian Sheepdog (aka Albanian Sheep dog, aka Sarplaninac) watching herds of sheep with great success in Northern Albania. I was always warned to not get near one especially when they were guarding sheep whenever I visited family up north. They're great tempered with the family they grow with but anything else they consider a foe. Check out this old video of 2 of these dogs taking out 2 wolves.
I can't speak about the authenticity of this particular video, but i have personally seen/petted/my SUV attacked by Sarplaninac dogs (i lived in Bosnia for 7 years). They are *HUGE* - in the 120-160 lbs range and seem to fear nothing. There is another 'sheep-dog' in that part of the world called a Tornjak (a Bosnian breed iirc) and they are very large as well - though i haven't seen as many of them as the Sarplaninac.
I really wanted to get a Sar (to bring back to the States), but it just didn't work out. They look like a canine version of a lion. They don't bark unless there's a reason and then i'd rather not be on the wrong end of it! As to whether a Sar can kill a wolf or not is unknown to me, but i heard about an incident where a pair of them kept a pack of wolves from killing sheep one afternoon near the village i lived in for 2 yrs.
