Thanks all for your guesses. I am beginning to despair of figuring out how to validate guesses, given the uncertainty in my own values, and figure out who came close enough first. I will post my "answers" here, and hope that I won't be pressed to name someone as the winner, or to defend my numbers with especial vigor.
(1) The profit on a gallon of gasoline earned by a gas station in the U.S. during 2011.
My number was $0.05. flagamuffin seems to have the right idea, that gasoline is mainly a way to attract people to shop for snacks, but it is not quite a loss leader. Forbes says the profit was a dime at the beginning of this year, and a nickel the year before. I don't think this number surprised me too much, but I probably would have guessed higher. I have pointed out to people that bottled water (that stuff that occasionally falls out of the sky in large volume) is more expensive at gas stations than gasoline.
(2) The profit on a gallon of gasoline earned by ExxonMobil on gasoline sold in the U.S. in 2011.
The "correct" number here was an astonishing $0.0033. This value is hard to verify. My number was provided by ExxonMobil for "the fourth quarter of 2011," which may be a carefully-selected time. The number goes up to eight cents for the first two quarters of 2012. I tried to do some plausibility checks based on ExxonMobil market share, gallons of gasoline sold, and reported profits, but got bogged down in all the complications.
(3) The combined local, state and federal taxes on a gallon of gasoline sold in New York state in 2011.
I put it at $0.656, based on the American Petroleum Institute. Another source gives $0.473 for state taxes only, and the federal tax is now $0.184.
I might have guessed a bit higher, though not as high as some of the guesses here.
The idea for this quiz came originally an article by that obnoxious John Stossel.