Group ride or coming up on a cyclist who apparently knows how to ride: "On your left" ...or if I'm part of a group passing, I'll add how many of us there are, or if I was the last one. People seem to appreciate that.

If I'm coming up on a Dorkus Oblivius swerving all over the road, a young kid on a path, or someone with wires dangling out of their ears: I'll whistle well in advance, or shout "Oy!" -- seems to grab their attention far better than 'passing on your ___'

If I pass someone with earbuds who didn't hear any of the above - I'll get Quite Vocal as I pass & their eyes get hugs.