I think the only time I was bitten it was by some little yappy thing - fortunately too small to do significant damage.

Of course, I should have been bitten when I jumped in to rescue my little dog from a usually mellow very large shepherd that had suddenly attacked him - no idea why I didn't get seriously hurt. Learned later that the shepherd had just returned from doing stud duty and therefore had an excess of dog testosterone, and he was fine the next day when we walked by (though my little guy was pretty nervous around him for quite a while).