sound effect -
By Ethan Nebulae -

Ok, this is awesome.
First, you need something metal. I just happened to pick up a machine
head(tuner(whaterver you call it)) that was laying around and I 
lightly tapped the strings and it made a sweet sound. So, if you 
happen to have one of those get one. Or some other smooth metal object.

Next, use your left hand to mute the strings toward the head. Then
just lightly tap or slide the thing around on the strings (the 
first 3 strings work the best.)

Then just experiment with it. ô¿ô