[ivymike1031]

here are some numbers that ought to add to the confusion:

From Engineering Fundamentals of the Internal Combustion Engine, Willard W. Pulkrabek, 1997
Heating values of various hydrocarbon fuels (HHV, LHV), in kJ/kg, molecular mass, in kg/kmol, stoichiometric AF ratio, octane numbers (MON, RON):

Gasoline (similar to C8H15), 111, 47300, 43000, ~14.6, 80-91, 92-99
Methane (CH4), 16, 55260, 49770, 17.2, 120, 120
Methanol (CH3OH), 32, 22540, 20050, 6.5, 92, 106
NitroMethane (CH3NO2), 61, 12000, 10920, 1.7, -, -

So if you look at the energy released by the fuels (w/o regard to the engine), it would seem that Methane has the most bang per unit mass. If you look at the energy released per kmol of the fuel, you get the following (HHV only):
Gasoline: 5.250E+6 kJ/kmol
Methane: 0.884E+6 kJ/kmol
Methanol: 0.721E+6 kJ/kmol
NitroMethane: 0.732E+6 kJ/kmol

Gasoline comes out on top in the "bang per molecule" category, with a six-fold advantage over the smaller molecules.

But wait, there's more:

If we look at the amount of energy released for a given mass of air (more like what you'll have in an engine, but still ignoring compression ratio and the air displaced by the fuel, again HHV only):

Gasoline: 3240 kJ/(kg air)
Methane: 3213 kJ/(kg air)
Methanol: 3468 kJ/(kg air)
NitroMethane: 7059 kJ/(kg air)

If you take into account the higher compression ratio alowed by Methane or Methanol (not sure about N.M.), they begin to have an advantage over gasoline (excluding the effects of the fuel displacing air).

So anyway... it was a tricky question. My answer is that nitromethane releases the most energy per kilogram of air, while methane releases the most energy per kilogram of fuel, and gasoline releases the most energy per molecule. Nitromethane releases the most energy in a given engine, and I suppose that's all that matters here.