Poster of Greenpeace about Electrabel (the electricity company):
And this is the best: not far from where I live, there is this building where people use to stop and take photos as it is mentioned in some guides as a "Horta Building" (Victor Horta is a very famous art nouveau architect). The owners claim that the building is not by Horta and are fed up with the buses and crowds taking pics. So, they decided to put this sign.. the result is that now there are even more people taking photos... including me, of course!
(some argue that Belgian sense of humour, as I call it here, is driven by surrealism, one of the most famous products of this nation. point taken!).