I had a minor issue with a SUV early today. It pulled a left turn directly in front of me so I had to do a quick stop at the green light. It didn't just turn green, it was a stale green for me. So I tapped my OEM horn/bell ringer

several times and he actually look back at me. The kind of look like whats my problem. Like I almost met your side door kind of problem.
Anyway I do believe that at least when its warm, the OEM horns do work, especially when tapped over and over rather than a single blast or toot.
I for got to do this at the intersection above, but I'm getting in the habit of turning my brights on during the day on and off just prior a intersection, if I'm going straight. Its not much but I don't see it making me more invisible.