When i'm playing the bass, one technique which I particularly like is to fret a note, and then to tap on the string i'm fretting at various positions on the neck. I don't tap hard enough for it to be called "tapping" as you don't hear the note which my right hand is "playing". What you do hear are extra harmonics and generally pleasing frequencies which aren't there when plucking or picking, or even when using artificial harmonics in the style of an 80s guitarist. This works particularly well on acoustic bass.
So.... what's the name for this, who else does it, and where's the obligatory amazing youtube video of the master of this technique?