What are the worst/stupidest conspiracy theories you have heard of?

There are so many conspiracy theories out there and many people are actually stupid enough to believe them. These are my top 5:

1. Bush planned 9/11
2. US faked landing on the moon
3. The earth is flat
4. Holocaust didn’t happen
5. JFK assassination was an inside job.

that the earth is flat. how can anyone seriously believe that in this day and age? it is just unbelievable.