This lamp by designer Jethro Macey requires you to insert a coin before it lights up.
Coin Lamp is the first product in a range based on the concept of values and reward, it subtly heightens awareness of consumption through design.
No need to be subtle about it. This is exactly what I need to teach my kids not to leave every light in the house on! Put these in every room, and you can use the coins to help pay for the electricity bill at the end of the month. http://www.jethromacey.com/shop/products_coin_lamp.php -via the Presurfer