DeepBlue, an MIDP game for the 7650 in which you have to destroy nuclear submarines (sounds eco-friendly to me...). It is a good example of a small price for a small game, it costs just $3. Available via Handango.
Originally Posted by Handango
You are the Captain of a fleet with an important mission in the black sea: check and destroy secret nuclear submirenes in this part of the world. Your mission is to find and destroy all the subs located in this deep sea. Destroy enemy subs before they destroy you. Explode them with slowly falling depth charges while avoiding their mines. There are several kinds of sub each with different ways of moving and shooting.