It depends on how crazy and/or meme-able it is. Personally, I can't get enough Alex Jones memes.
My real favorites are not necessarily conspiracy theories in the strictest sense, but groups that with a lot conspiratorial thinking. In no particular order:
The Sovereign Citizens are a group that thinks they can make their own license plates and cite the Articles of Confederation and 18th century Admiralty law to get out of traffic tickets, because they're not driving they are traveling, also see 'I'm a being detained'.
The Reichsburgers claim that the current German government, and every German government since about 1919, isn't actually a government, but a corporation and the real German government in exile some where; they are right about one thing, second reich = best reich.
Hotep, Kemet, Hebrew Israelites, and a few others; on the 'calcified' side is that ancient Egypt was predominantly populated by black sub-Saharan Africans, on the woke side is We wuz: Kangz, Vikings, Samurai, Shakespeare, de Vinci, Beethoven, etc. Also see 'decalcify your pineal gland' and Hidden Colors (and while your at it Tariq Nasheed).
Memes aside, conspiracies do happen.
Coups are almost always involve a conspiracy.
Secret societies have been used to plan revolutions (the Carbonari and Union of Salvation).
Government officials have been parts of conspiracies before.
False flag attacks are a thing: Operation Himmler.
Governments have lied to the public, especially when trying to justify wars; see USS Maine, .303(and probably more war material) on board the Lusitania, the Gulf of Tonkin.
There are a few 'conspiracies' that are fairly plausible(means, motive, and opportunity).
It wouldn't really surprise me if the 2016 coup attempt in Turkey was a false flag attack to justify the subsequent purges and consolidation of power. My suspicion comes from the dumpster fire that was that coup; no serious attempt was made to kill or capture Erdogan, and critically they failed to prevent Erdogan from addressing the public.
The other one is the recent chemical attack in Syria, in short why? Imagine you are Assad, the war is winding down, the international community has pretty much rejected the idea regime change, I know lets do the one thing that could provoke intervention against us. Makes total sense right. On the other hand foreign intervention is the best chance the rebels have, and they almost certainly have access to chemical weapons that they captured from the Syrian government, making framing them that much easier.
Basically conspiracies do happen***, but I'm mainly interested in the memes.
By the way Atrazine induces complete feminization and chemical castration in male African clawed frogs
The chemicals aren't turning the frogs gay, there turning them trans.