The government's data on gas guzzlers is pretty funny. Uncle Sam's EPA rankers are about as knowledgable about cars as Pete Carroll is about goal line play calling. Case in point, the EPA considers a Rolls-Royce Phantom Coupe to be in the same class as a Prius, and an Aston Martin DB9 to be in the same class as a Scion iQ. Riiiiiiiiight.
With that in mind, the most fuel inefficient cars in America across every category are all perfectly desirable vehicles that anyone would enjoy to have in their garage. And here's that list. Though, interestingly, the Hummer isn't on the government website. Apparently they're keeping the list to cars that use the miles per gallon metric, not gallons per mile.