No other than Greenpeace has identified Nintendo as the worst company on earth as far as eco-friendliness is concerned. Greenpeace rated Nintendo 1.8/10, making them the company that has been killing the planet, in a manner of speaking.
Other than Nintendo, they are keeping their eyes on other tech companies as well. This includes Dell and Lenovo. On the other hand, Nokia and Sony Ericsson are getting thumbs up ratings for their eco-friendly drives. The full report is available at this link in case you want to read it.