Two intriguing examples of persuasive design encountered at ENSCI in Paris:
The first one, next to the stairs, is an invitation to use the staircase as opposed to the elevator so "harden your butt".
The second is a sticker that someone have put on the toilet hand dryer. It says "What's the largest contributor to global warming?" with two answers: "Dry one's hand with a tissue?" and "Press a button?".
Subtle cueing to invite for behavioral changes.