I have two of the largest dogs in the world. Irish Wolfhounds. They love kids.
TABLE 1. Dog breeds and crossbreeds* involved in dog-bite-related fatalities, by 2-year period -- United States, 1979-1996 +
these are the cdc stats on breeds involved in fatalities. the columns didn't line up right, but at least it shows the relative order.
however, you might have to divide the cdc numbers by the number of individual dogs of each particular breed that live in the US to get a true measure of dangerousness.
and of course, these stats don't control for craziness of owners.
i don't see Irish Wolfhounds anywhere on this list, so i'm guessing they were not bred for viciousness.
some breeds of dogs were probably bred for traits like intelligence and gentleness, but i don't know enough about dog breeds to know which ones.