While doing a bathroom remodel I came across this 220 volt wire to the clothes dryer on the other side of the wall. the last time a shower stall was installed, somebody put a nail for a trim piece right into a hot and a ground conductor! It burned the end of the nail back before tripping the breaker or burning the wire in two, so everything still worked.

Note the black mark in the 2 x 4 where the hot nail was! Did I mention this was a shower? With water! Nobody got zapped.