Warning: Troll Alert!! I'm sure I'll get modded down for this but...
I would think that the latest spate of HiFi speaker wires would be right up there. The key difference between dowsing rods and these cables, is that once in a while dowsing rods seem to work. The multi-hundred dollar cables, time and time again in double-blind tests, have been shown to perform more poorly than the cheap utility speaker wire. And yet, there's a whole industry out there that argues (and markets) to the contrary.
Snake Oil indeed.
A sine curve goes off to infinity, or at least the end of the blackboard. -- Prof. Steiner