If there's one thing people hate more than BMWs and SUVs in general, it's the X6. But people also hate hybrids (granted, usually not the same people). So guess what? BMW made a (somewhat obscure) hybrid X6 with 480 HP and 18 mpg. I've been tempted to find one just because it's the confluence of so many types of petty hatred.

One thing to think about is that the effect of a vehicle on the environment depends not just on the mpg, but on how far you drive it, and how many people you transport on average.