The one from the Baskervilles is still to be found

Difficult to tell, I tried to check and there is no precise breed for it. "the animal belonged to no known breed. Rather, the creature was meant to be the embodiment of an ancient myth about  Death’s dog. When Sherlock Holmes’ sidekick, Watson recalled the moment he could check out the animal’s corpse closely, however, he describes the creature as half-mastiff, half-bloodhound."About the St Bernard, Cujo is terrorizing Castel Rock, Maine or you have Neil the martini-slurping in Topper.  I wonder which of the two is the scariest!

Cujo was definitely a St Bernard.  Have you not seen the movie?

I watched it in high school when I was busily devouring everything by STephen King I could get my hands on.  On VHS no less, probably from Blockbuster 8)