I've heard stories that Newfies "rescue" kids from swimming pools, and have to be trained to not do that. ;) My cousin had one for many years, and the only problem was finding play balls big enough. She became expert at retrieving halff-swallowed balls from doggies throat.

I have to mention coonhounds as a possibility, too. They look like a doberman/bloodhound cross, but the great part is people mistake them for rottie or dobie mixes, and stay far away. They also mistake the coonhounds friendliness as aggression. Like bloodhounds, coonhounds might lick you to pieces, or knock you over trying, but that's about it. They also have a rather.... ummm... crazy look in their eyes when excited. The downside is, they'll eat your furniture and half the yard. They get bored easily. Oh, and they climb. Tables, trees, benches, cat trees... and they open cabinets and refrigerators, and can chew through cans to suck out the contents... .

Come to think of it, Yorkies and Chihuahuas do a good job of guarding. ;)  

Hey, Bryster, how are the grooming chores for Newfies? Beautiful, beautiful dog.