4. Wilson is Evil
At one stage during House's hallucination is the real finale, its suggested that Wilson acts as his conscience, meaning he never hase to grow one of his own. Then we forget all about that for some nonsense about House escaping an exploding building, presumably through witchcraft. But that should be the real revelation - Wilson is the one preventing House from becoming a good human being. It has the advantage of being so mind-blowingly awesome it would take weeks for anyone to realise it makes no damned sense at all, much like the Sixth Sense twist. Bonus points if Wilson actually goes evil and puts on a fake felt goatee.