Uhmm please, pretty please? I think you're a nice person and not a cynical hollowed out shell like the rest of us NESers....
Close enough.
Imagine you've got a mobile generator you're hauling around in motorized vehicles hooked up to the engine, much like on an old U-Boat, and you've got capacitor banks for storing up charge. Suppose you want to use all that electricty to fry some people. But it's hard to direct. So you carry around tanks of gallium and high-pressure pumps to spray it like on a crocodile flame tank.
Why gallium? For one, it's only ten times less conductive than copper wire, and is easily coverted into a liquid form at about room temperature; you can heat it by using it as a coolant for whatever power unit you have on board. Plus when you spray it everywhere it gets into the soil and can be reprocessed out, and in the meantime it's not anywhere near as toxic as mercury (though for some people, that might be a drawback). Secondly, gallium has the unique property of attacking metal lattices. Meaning it eats metal over time.
Put the two together and you have a perfect if somewhat short-ranged anti-armor weapon that's also somewhat reasonable at frying infantry. Because of the corrosion-resistance needed for the barrel already you can also use salt-water (which is also conductive though tens of thousands of times less so) in a pinch should you run out of the stuff.
It's like an electrolaser without the laser or those weird hydroelectric nonlethal guns they've developed lately on it's rather quite lethal. Actual problems with the system include 1.) finding enough gallium, which is quite rare, 2.) getting compact power generation and storage powerful enough to afford such a thing, 3.) having auxiliary units following soldiers around reprocessing the stuff off battlefields, 4.) actually finding conditions in which to use it where it would have some real benefit over conventional weapons, which would be very rare.
Still, it was fun. And no, as a note to any mod considering letting their player run with it, I don't think you should, for the above-mentioned reasons. It'd mostly be a psychological weapon if anything. Chief benefit would be directing attention towards the premise of Directed Energy Weapons. Still, it's about the best you can do in a 1930s equivilent.
Anyway; Sympth, how do you do Espionage?
Quietly.
(forgive us, we're Canadian)
The net gain was much worth it. 
