As the title suggests, let's talk blunders
Speaking for myself my worst mistake probably was an involuntary one, back in those days when there was only Airfix and no Internet, and all the available information on Napoleonic uniforms were the books by Funcken and Philip Haythornthwaite, which soon became my "Bible" on Waterloo. And there was this nice picture of a subaltern officer of the 23rd Light Dragoons, in white trousers, Hungarian boots and a sky blue Dolman with white cords, looking way more dashing than the rest of the lot. So much so that Minifigs produced some metal Light dragoons based on Haythornthwaite's description which I promptly bought and painted, even though they were much to big next to the Airfix minis. Alas, as can be seen by consulting the centjours page, it was all an error. They most probably never had a sky blue uniform nor did they wear anything remotely similar at Waterloo, but just the regulation dress common to all the other regiments. Pity.