Oh, yeah! The horn. Mostly used to attract the notice of someone a person knows while they are walking along the pavement
It's actually a really useful piece of kit, for all sorts of situations (including approaching blind bends on narrow country lanes). I usually have my thumb over the button (plus a finger on the hi-beam flasher) when I am about to overtake, amazing how that can save your life on occasion - especially on dual carriageways.
A mate of mine had an air-horn wired into his ZZR1100 - if he used that sucker, there was never any chance of a "didn't see you mate" (more a case of "I can't hear anymore, mate!"). Are such things legal? I'd like one.