A tambourine is perfectly legit, as long as it's used as an instrument, not a noisemaker. And I'm not saying you have to be a pro, either.

I can't imagine "Never Ending Song of Love" without one.

If it's only to allow non-musicians to participate, I think just singing along, hand clapping, or foot stomping is fine. It's also fine if you're dealing with kids and you want to encourage participation - fine.

But, if somebody I've paid to see puts on those ankle shakers and starts handing out rattling eggs, get out of my way!