None. All those I believe in are not theories, they are based in fact. Like, 9/11. No "theory" it Was an inside job.. I trust a Chicago Fire Chief, FDNY fireman's eyewitness accounts, engineers, architects, videos of LSC's going off, Mark Louseaux's professional experience. Our Govt might have a reason to lie, but these men Don't. Why testify it was an inside job? Why not take Safe route and lie it was the work of 6 lone Arabs? That burning JP-4 can :"melt steel and concrete"?
By Whom, and Why, now, that can be tossed about.
The Roswell Cover-Up. It is definitely a very Sloppy cover- up of something.
What and why can be bandied about but it was big enough to scare the US Military.
JFK's assassination. A Fact at least two different shooters. A Fact govt somehow involved or Warren Report wouldn't have been sealed 50 years.
Also; who, why, is a CT.
https://www.youtube.com/watch?v=axM3auVJnIY