While attempting to install a header with lifting eyes onto my garage ceiling, I was drilling into the ceiling / roof truss when water started shooting out. SHIT! Turns out I drilled into a hidden water line which was above that very truss member.

After immediately shutting the water off to the house and releasing any pressure, I cut a hole in the ceiling drywall, found the hole, ran out to Home Depot for some PEX tools, and a junction, and had the water back on in about an hour. It wasn't that bad, but was a blow to my morale. :-/