First thing I found, while tracing a door bell wire: a dangling, fully energized 120V line, just cut off and dangling in the HVAC duct work! Yep, I was trying to figure out where the bell wire went, and while doing so, I came across a piece of BX just up between the floor joists on top of a HVAC duct. I thought, "Hmm, this is odd, I wonder it it's hot." My hand started to move and then I thought: wait, check it first. There was about 6 inches of wire coming out of the cable, just snipped off. I took a pen tester, held it up to the bare wire and... beep, beep, beep!!!
Great. God knows how long it had been up there. Just being a conservative and cautious guy, I put wire nuts and tape on the end and terminated it in a box.
Being a curious guy, I looked around some more and found, well, this. Seems a few too many wires in this small 4x4 box. I didn't take the cover off, for fear that I would not be able to get it back on. Sigh. Somehow, I think these situations are far too common.
Is this sort of thing all that common? In every house I've owned, I find stuff like this.