The only time I use a bell is on the MUP, which I don't ride often. I like the Timber mountain bike bell because it can be flipped on to ring continuously. Sounds like a friendly ice cream truck. Works well, other than with folks using earbuds or headphones. And I can keep my hands on the bar.

I got the version with the rubber band strap and can find a place to fit it on all of my bikes. Tilting it roughly controls the ringing frequency and volume. Tilt it a bit more for smooth pavement, so even minor ripples will jiggle the bell clapper enough to be effective.