I've had
this one for a couple of years now. Bought it because I'd been run off the road twice in one week and even laying on the puny factory horn, the other person seemed oblivious. I've got it hooked up to function with the horn button (steering wheel) and is even loud enough to get the attention of semis.
If you're light enough with your presses you can still give the soft(er) courtesy honk too.