I recently started playing World of Warcraft again and forgot how utterly annoying this tiny little clockwork gnome was. I decided to silence him, and I figured I might as well share it with everyone else. He uses Mechanostrider wound sounds, so if you fight a Mechanostrider, or someone riding one they may not make noises anymore.
This is NOT like your normal addon, you do NOT put it in the Interface/Addon folder, instead you extract it to the root of your WoW folder. After you're done, you should have Sound folder along with your other folders in the root directory (WTF, Interface, data, etc.)
If it doesn't work in the root try extracting it in one of these locations instead:
*World of Warcraft Directory*\Data\
or
*World of Warcraft Directory*\Data\enUS\
No more loud gnome vendor!