Oh yeah I thought of another one I believe in. The CIA was involved with trafficking drugs into the USA through the 80s/90s to fund a war in Central America. Interesting to note this was a time when the "war on drugs" was in full swing.
I wouldn’t even put this in the category of conspiracy theory anymore—though at the time Webb was treated like a pariah/lunatic and drummed out of journalism, leading to his (alleged) suicide.
It’s pretty well established now that the CIA was doing this. (Note: The excellent TV series Downfall—not the movie about Hitler’s final days—is about this topic, as is a Hollywood movie starring iirc Tom Cruise.)