When I come to a stop sign and hold the brake a rattling sound starts. If I put it in park or neutral the sound stops. Ideas?

 

Any times that this has happened to me it was due to my cat rattling because it was rotted out and needed to be replaced. Currently I have these symptoms and one of my exhaust tail pipes are vibrating too close to the frame and causing the rattle.

In each of those situations, it only rattled in drive when stopped at a street light or wherever (lower idle than neutral and park).

 

Converter is a good guess. But it could be anything that vibrates at the same resonance as the RPM when you have it in gear. Heat shield or loose interior trim are other possibilities.