I consider these to be more like "red herrings" than riddles, but I suppose it's the same concept. Here's one I heard recently but I'm reciting it from memory... it's also eerily familiar to the story of the Australian yacht with the ripped sail:
A large party yacht was found drifting hundreds of miles from land. No one was on the boat, yet it had been left with all of the passengers' belongings. Surrounding the yacht were the passengers, dead, floating in the water.
If you're a battery, you're either working or you're dead....