Given my innate cynicism, I'm almost ashamed to admit that I can detect (or perhaps I should say "have detected") undergound services by dowsing, using a couple of lengths of welding rod with a 90degree bend at the end.
I used to work as a college technician, and a few of us tried to find a supply cable running under a field at the back of the college. Some got a response from the dowsing rods, some didn't. Later we tried the same with looking for the water supply and main drain. Agin some could, some couldn't, but not the same people. I was the only one who could detect all three, which amazed me.
Before this test I was absolutely convinced that dowsing was superstitious mumbo-jumbo, but I'm now convinced it works. I suspect the reliability might be about the same as that of a neon screwdriver though...