I have one of those little Daisy bb / pellet pump guns (the one that everyone has had at some point in their lives). I use it all the time to drive off the neighbor's goats. Those suckers refuse to leave or run away - they'll just kind of stare at you as they munch on the roses on the front porch.
So I pump that thing up a pump or two and fire away. The bbs just bounce off them, but they get the silly critter's attention. Sometimes have to fire at them several times to really get 'em moving [img]/forums/images/icons/smirk.gif[/img] .
But that little Daisy only cost about $25 and is kind of fun. Very effective for certain things...