My Land Cruiser's V8 engine is making a weird noise, any suggestions?

I've been driving my 2007 Land Cruiser with the 4.7L V8 for a while now, but lately it's developed this weird knocking noise when accelerating or decelerating. The noise is more pronounced when cold, and seems to come from the engine area. I've checked the fluids, oil pressure, and belts, but couldn't find anything out of the ordinary. Any suggestions on what might be causing this?