Let's add two really big ones, shall we?
Watergate
Iron-contra
Iron-contra? Iran Contra is already on the list.
And some I would take off the list:
Waco
Ruby Ridge
JFK, of course
Building 7
Bohemian Grove
If we keep Bohemian Grove on the list then we should add the Free Masons, the Illuminati and the Elders of Zion. I would tend not list fraternal orders, even ones with secrets, be they real orders or fictitious.