I tend to "mute" all combat related sounds (hits/parries/spells etc etc) so I only hear boss emotes. As Blizzard does not provide a feature like that in their client, the only way to do so is to replace sound files in your wow folder with empty ones.
Anyhow, I was sifting through the sound files and can't find the annoying rogue ability Shadow Blades (http://www.wowhead.com/spell=121471).
If you don't know what I am talking about, it can be heard here:
Now my plea is: does anyone know what sound file (location/name welcome) that this ability uses?