A good yell, from deep in your belly, can stop a car.
I've stopped cars on several occasions using my voice. When I took tae-kwon-do years ago, we were taught to project loud yells...they help to firm up your diaphragm in case of a counter-strike, and they can disorient an opponent and project quite a bit of power. IMO, it works. And it doesn't require any more junk hanging on the bike.
Note: for peds, I've found a bell works best. It's instantly identifiable as a bike, carries a long ways, and seems both civilized and friendly.