Once while riding in a rundown
section of San Bernardino, CA I
attacked, more or less by a pack
of feral dogs... a couple of mangy
but NOT LEAN GSDs, a Rottweiller
and a couple of mongrels and went
right out and bought one of these:
http://www.securityprousa.com/50vostba.html

I have never ridden with it, and I haven't had
trouble with dogs since, but that one occurance
was enough to fear I was DOG MEAT! :O)

I now keep the unit in a bottom drawer
w/o the batteries in it and would hate
to use it on most humans.