The picture I've chosen is A Grotesque Old Woman by Quinten MASSYS (1465 - 1530).
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It really jumped out at me, and is apparently based on an old cartoon by Leonardo da Vinci. For me this painting could come staight from the cover of a Terry Pratchett novel, and this style of cartooning is even more savage than some stuff around today.
The picture itself is a satire (my kind of humour) of women who dress far younger than their years. Quite appropriate as most of the nighclubs in the UK seem awash with this kind of divorcee nowadays. Apologies, went a bit Daily Mail there. Anyhow basically this painting is mutton dressed up as lamb.
Or maybe Tony Blair in a wimple?
Other paintings that made it close to the list were:-
Madame La La at the Cirque Fernando - DEGAS, Hilaire-Germain-Degas
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The Fighting Temeraire - TURNER, Joseph Mallord William
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Allegory of Love II (scorn) - VERONESE, Paolo
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Anyhow if you get time, go to the gallery, it's free, and there's some paintings there that are worth way more than Cristiano Ronaldo's transfer fee, which is quite impressive really.