I like it when perfectly reasonable signs appear under ironic circumstances, e.g. a low-flying aircraft sign leaning at a 45 degree angle.
Or when things are just plain silly, e.g. the biohazard reveal in the Red Dwarf episode "Quarantine."
There are also these little signs at the train stations at Disneyland that appear to prohibit dancing on the train. I presume they want people to remain seated, but still....
