To be honest I don't really have any of my own theories, all of the the theories in my head were put there by various parts of the media but mainly watching too much TV.
Theories about activities, examples: how to help prevent an airliner for being hijacked, how to evade enemy capture, how to boil an egg etc.
Conspiracy theories, examples: aliens/abductions, the unknown, parallel universes etc.
Obviously I haven’t listed all the theories that have turned up in the media, but should be enough to give you an idea of the sort of theories that have been bought to my attention.