Rattle is driving me wacky!!! Help!

I have a 2001 Silverado, V8, A/C, auto, 2WD and I've got a rattle somewhere inside the driver-side dash area that is driving me wacky. I've popped off the trim bezel and have removed the instrument panel cluster and looked and felt all around for ANYTHING that might be loose or bumping something and is the cause of the rattle. I've not been able to find anything that appears to be the source of the rattle. The sound is definitely a rattle, not a squeak. It is not an all-the-time rattle -- it only occurs when I hit a bump. Anyone else with this problem who found the source of a similar rattle? I sure would appreciate everyone's thoughts. Thanks to all who read and especially to anyone with suggestions. -- old_car_eddie