Silence...

I've never had a horn on any of my bikes that got the point across. The horn on my Speed Triple has always worked, but it makes a comical kind of "meep meep" sound. Pretty embarrassing actually. Doesn't exactly convey the right point, its like ":hello2:, excuse me..."

I typically just rev the engine at them. Its more like :finga: ! I think it gets more attention than any horn would, heck of a lot louder unless you mount an air-horn. Faster too, you're already holding onto the throttle and clutch. Sure, they think I'm an a-hole, but if I get to the point that I feel the need to rev my engine at them then they probably deserve it anyway.