Easily the best April Fool's gag of the day came in this Tory spoof of a typical Labour propaganda ad. (even with the extraneous disclaimer at the end). It's genuine satire, and it's its core of truth that makes it so irresistibly watchable (that and Mr Cholmondley-Warner's reappearance after all these years, as Benedict Brogan points out).
A close second comes Dizzy's April Fool's gag about subcutaneous ID chips which, I'm highly embarrassed to admit , had me hook, line and sinker. Well, it was last night. It was late! I was tired!! Anyway, it's so scarily plausible, I think it short-circuited my 'common sense' wiring and activated the gullible processor.