How to empty the queue of pending notifications?

I have a .desktop file that I use to kill the notifications.

[Desktop Entry]
Name=Notify Kill
Comment=Kill those pesky notifications!
Exec=killall notify-osd
Icon=utilities-terminal
Type=Application
StartupNotify=true
OnlyShowIn=GNOME;Unity;

Toss that as notify-kill.desktop in ~/.local/share/applications, wait a minute and it will pop up in your Unity dash.

To use, just open the dash and search for kill or notify, and it will clear your notifications!