I thought about getting a louder horn a while ago. I can think of situations where it would be nice, but in an evasive manuver, I am with the others: I can't find it fast enough and then I have used up some valuable time.
If I still had quiet pipes I would go with an air horn. But once I put on louder pipes, I figuered if they can't here me now, they aren't going to hear the horn.
Plus, some people you just can't reach: Yesterday I was in the cage and a woman was driving at about 70mph with a flat rear tire. Tire was just about to start comming apart. She just kept on going. I watched for a little bit, then accelerated up to her. I was laying on the horn, literally hanging out the window, waving my left hand and screaming. We when on for about a 1/4 mile before she noticed me.....