I'll think of more, but please add whatever you feel like or mods you would like to see busted/confirmed.
Also, I saw an older Mythbusters last night that I hadn't seen before. They tested AC on vs windows open FE. I think their testing methods left a lot to be desired and they should have run it more than once, plus they only tested at 45 mph due to safety conditions on the track. Windows open won by traveling an extra 30 miles on 5 gallons of gas. It's a large enough margin that I'm certain it would be fairly consistent, but I'd like to see the same test at higher speeds (and swapping methods per vehicle, and repeatability, etc).