For all you budding vexillologists out there, Frosty showed me a terrible one today on IRC, and I just hate to think there are more awful flags out there that aren't getting the recognition they deserve.
Brown County, Nebraska (IRL)
Some real belters from Australia:
Melbourne City (This is actually inaccurate; the one on wikipedia is modernised and simplified. The real one has an impressively/frustratingly detailed sheep in the left corner)