"Passing through"
"Good morning" / "Good afternoon"
For walkers, often just coasting with my loud Campagnolo freewheel gets a reaction when I'm still quite a distance back.
'On your left' only for formal group rides, where the riders already know what it means. A random walker on a path doesn't always get it.
Also,
I use my right arm pointed right to signal a right turn. I used to occasionally get confused when the leader of a group ride put his left forearm up. Who was he waving at? Oh, it's a right turn.