Rattle underneath

Hey guys. 2006 Tacoma with 56,000 mi. And I'm getting a rattle underneath that's annoying as hell. Almost sounds like a heat shield rattling but I checked and that's not it. If I'm stopped with my foot on the brake it's really noticeable but if I shift into neutral it goes away. Any ideas what this might be? It's intermittent and isn't constant. Thanks for any suggestions.

 

Don't know, but I have the same rattle on my '13. Never have been able to figure it out

 

Could be the honeycomb rattling around inside the catalytic convertor. Have your buddy hold the brake and put it in drive while you crawl underneath. Set the ebrake, block the wheels, and make sure it's a buddy that you can trust with your life. If it's not obvious at that point, you need a mechanic's stethoscope.

 

I had pebbles in my 2nd cat heat shield right under the drivers seat, so i just removed it and all better.