BattleForge. Shouldn't being able to play a card-based game without the senseless murder of dozens of trees for actual cards be able to usurp at least Vampire Rain or M.C. Kids on Al Gore's Top 5 Games list?
Regardless, as of March 24, you'll be able to build a jetpack out of aerosol cans or perform whatever other eco-terrorism you like, because BattleForge will be doing enough environment saving for all of us. It's got that ish locked down. That said, if you really want to be an EnergyStar, you can hop into the beta right here.