Clicking upon acceleration

I've noticed a few times lately, when I'm accelerating, from most speeds, when I start to get on it, and the truck is kind of lowering in the back, raising up front, from acceleration, I hear a metallic click or snapping sound. It's not really loud, and it's inconsistent clicking.

I checked underneath, and nothing is hitting the driveshaft, and nothing seems to be loose. The only thing I can think of is my skid plate is kind of loose, but it sounds like its coming from the back. My springs have been squeaky, but it seems to be a different sound than squeaky springs.

I'm just wondering if anyone else has had this happen, or if they know what it might be. I hope it's just something simple, that I might have overlooked. Any ideas?