He built a 600hp 60mpg Hummer.
http://www.neatorama.com/2007/10/21/...iendly-hummer/
Here's a more in-depth article, very interesting read.
http://www.fastcompany.com/magazine/...d-messiah.html
I think that's pretty amazing, and it doesn't even sound that complicated, especially if someone started a parts market for it.
(Sorry, I know I've already posted these links in a different thread before, but this is so awesome that it deserves its own thread.)