I'll start with the classic "The Earth is flat, and the government is trying to convince everyone of this to control us and turn us against the Bible."
The whole "the moon is a hologram projected by the Illuminati to control our minds" theory is one of my favorite pieces of Internet batshit to share with others.
Anyting on the Secureteam10 youtube channel because that guy is either insane or an expert at making ad revenue from hundred of idiots/curious onlookers. also just occasionally between the lizard people he randomly hits on something interesting and believable like the fact that all that tracking data Fitbit released the other month shows very clearly that there's an unregistered Russian facility in Antarctica.
One obscure theory I've heard about was that Waco was Sieged and burnt down because there was a CIA Airfield nearby and they saw something they weren't supposed to.
Laugh at - Roswell Saucer Crash
Buy into - none
Enjoy - Flat Earth, it's just so darn easy to disprove, yet it persists because some people want it to so badly, it's the perfect description OF a CT.