Truthers and chemtrailers are so incredibly angry they are no fun to talk to. The latter also has the problem of being completely insane. There is no logical debate with them.
I know a lot of people have fun with JFK theories, UFOs, ghost sightings, ESP, cryptozoology, and the like, but my preferences are towards things that have at least a little bit of technical "meat" to them.
Climate Change Deniers are only mildly interesting to talk to, as they are major goal-post shifters and are always trying to pull the "but that was last month's argument" on you. Creationists are great fun; their knowledge of science ranges from unbelievably bad to almost-good-enough to fool a college student. If you shop around on them, you can almost always find one that is a good contest.
And, yes, the Creationists do manage to come up with some of the most knee-slappingly funny ideas ever. T. Rex gnawing into a coconut. The first elephant to evolve searching in vain for the first FEMALE elephant. And let's not even get started on the Ark. The main problem with Creationists is they have no shame. They will lie, outright lie. Even when you catch one at it and make him admit it, he'll just move to another forum and repeat the same lie to a fresh batch of suckers.
So, for the best value of your entertainment dollar, I nominate the Apollo Hoax. Sure, the silly situations aren't quite as belly-laugh stupid (Polar orbits, say. Or rockets that melt because there is no conduction in space). But there is plenty of fun science to get your teeth into. Plus, out of all the wild conspiracy theories out there, only the Apollo Hoax crowd has consistently staged themselves into trying to argue their case from a scientific and technical basis (instead of delving into the murk of motivations and politics and meaningful stares, where entire nations could be hidden).
