I spent 4 hours last Saturday looking for a rattle that turned out to be a socket I left in the engine bay
Last Saturday I tore apart half the dash in my 2006 Civic chasing a rattle that showed up after I did a timing belt job. I pulled the glove box, the kick panels, even the center console, and found nothing, so I started thinking a heat shield or a motor mount had gone bad. Around hour four my neighbor wandered over, poked around the bay for ten seconds, and pulled a 10mm socket off the frame rail where I had left it wedged. The rattle was my own socket rattling against metal the whole time I was driving around blaming the suspension. I felt like a genius. Now I do a tool count before I close the hood, and I still lost a 3/8 extension last month somewhere in the same car.