Quote Originally Posted by TsPoet
This thing stops almost anything in its tracks (at least temporarily)

http://www.deltacycle.com/product.php?g=1

(note, that's just a random website where they are sold, don't know anything about that company).

I've also seen it used to stop a wandering car from continuing its way into a bikes way, the driver stopped dead.
very loud.
Yes, this is the airhorn I have now too. I have only had to use it ~4 times on dogs. All but one retreated/stopped in their tracks. One continued to chase -- I wondered if he was deaf. I got mine from Nashbar but they may not carry them anymore.

Emily