I don't understand the random finger pointing. The point of the OP was that the US and Israel have the most obvious "will, motive and means" to do this. No other country in the world wants to see another nuclear nation, especially one as aggressive as Iran. However, only a few select countries have a resolve to actively prevent Iran from doing so.
Why go through every possible event no matter how improbable? Are we going to reduce this conversation to conspiracy theories? If we are, I'd like to throw Antarctic penguins into the ball game. Think about it, no one would suspect them. What exactly do they do every winter when they huddle en mass in the middle of an iceberg for 2 months? Perhaps shielding a laptop and satellite link under the guise of a ridiculous mating ritual? They could be plotting a global take over and this is a test of our civilizations defenses. They first target weakly guarded nuclear facilities and control simple equipment as a proof of concept for a larger scale attack. You can't rule them out, or are you saying you speak penguin and understand the motive of every faction in the penguin community?