Not strictly an example of interesting language use but I thought it was worth sharing:
I took this photo at London Bridge railway station.
The part of the sign with yellow writing constantly rotates, displaying three different messages in turn.
On the day I took the picture, one of the messages - and as I recall, only one of the messages - was appearing upside down, as shown. Brilliant.
The anti-pigeon spikes on the top of the sign confirm which way is up...